2024-03-29T05:47:12Z
http://docs.lib.purdue.edu/do/oai/
oai:docs.lib.purdue.edu:jto-1042
2009-03-04T15:52:24Z
publication:spsoaj
publication:sps
publication:jto
publication:eas
publication:ggrs
publication:librariespublishing
publication:easpubs
publication:libraries
publication:sci
publication:geopubs
A Review of NEXRAD Level II: Data, Distribution, and Applications
Huber, Matthew
Trapp, Jeff
2009-03-06T13:06:52Z
text
application/pdf
https://docs.lib.purdue.edu/jto/vol1/iss2/art4
https://docs.lib.purdue.edu/context/jto/article/1042/viewcontent/01__JTO_1_2__Huber_Trapp.pdf
Journal of Terrestrial Observation
Purdue University
oai:docs.lib.purdue.edu:easpubs-1000
2012-02-24T20:27:29Z
publication:eas
publication:easpubs
publication:sci
A global sensitivity analysis and Bayesian inference framework for improving the parameter estimation and prediction of a process-based Terrestrial Ecosystem Model
J., Tang
Q., Jing
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/1
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1001
2012-02-24T20:51:04Z
publication:eas
publication:easpubs
publication:sci
Characterizing heart rate variability by scale-dependent Lyapunov exponent
Hu, J
Gao, J.
Tung, W.
2009-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/easpubs/2
https://docs.lib.purdue.edu/context/easpubs/article/1001/viewcontent/hu.pdf
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1002
2013-06-26T18:26:36Z
publication:eas
publication:easpubs
publication:sci
Crustal structure across the central Alaska Range: Anatomy of a Mesozoic collisional zone
Brennan, P.R.K.
Gilbert, H.
Ridgway, K. D.
A first-order process in the growth of continents is the collision and accretion of terranes against continental margins. Collision leads to the formation of a suture zone between the accreted terrane and the former continental margin. New insights on the suturing process are observed from two receiver function transects across the Mesozoic Alaska Range suture zone. Three distinct crustal sections are identified from observations of crustal thickness, intracrustal discontinuities, and Vp/Vs: a northern section with ∼27 km thick crust of felsic to intermediate composition, a central section that is ∼37 km thick that exhibits intracrustal discontinuities and has felsic to intermediate composition, and a southern section that is ∼30 km thick and has a more mafic composition. We interpret these sections to correspond with the former continental margin (Yukon composite terrane), the suture zone proper, and the allochthonous oceanic terrane (Wrangellia composite terrane). The boundary between the Yukon composite terrane and the suture zone appears to be a subhorizontal discontinuity that accommodated underthrusting of crust from the suture zone beneath the former continental margin. The boundary between the suture zone and the Wrangellia composite terrane, in contrast, appears to be a relatively discrete, vertical boundary. The observed variability in the crust across the Alaska Range suture zone is likely controlled by the differing compositions of the terranes involved, which influences how each section responds to precollisional, syncollisional, and postcollisional deformation.
2011-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/easpubs/10
info:doi/10.1029/2011GC003519
https://docs.lib.purdue.edu/context/easpubs/article/1002/viewcontent/Brennan.pdf
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
receiver functions
suture zone
Alaska Range
Wrangellia composite terrane
Hines Creek fault
Talkeetna fault
Earth Sciences
oai:docs.lib.purdue.edu:easpubs-1003
2012-02-27T17:53:31Z
publication:eas
publication:easpubs
publication:sci
Elementary proof of the B. and M. Shapiro conjecture for rational functions
Eremenko, A.
Gabrielov, A.
2005-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/easpubs/9
https://docs.lib.purdue.edu/context/easpubs/article/1003/viewcontent/Eremenko.pdf
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1005
2012-02-27T18:01:07Z
publication:eas
publication:easpubs
publication:sci
Geochemical characteristics of naturally acid and alkaline saline lakes in southern Western Australia
Bowen, Brenda B.
Benison, K. C.
2009-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/easpubs/7
https://docs.lib.purdue.edu/context/easpubs/article/1005/viewcontent/Bowen.pdf
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1004
2013-06-10T18:51:43Z
publication:eas
publication:easpubs
publication:sci
Equivocal evidence for a thermostat and unusually low levels of coral bleaching in the Western Pacific Warm Pool
vanHooidonk, R.
Huber, M.
An ocean “thermostat” was recently proposed that limits Western Pacific Warm Pool (WPWP) sea surface temperature (SST) causing anomalously low coral bleaching rates. We analyze WPWP SST trends and bleaching using HadISST data and a coral bleaching database and find no strong evidence for a thermostat or for anomalously low bleaching. A region within the WPWP has a trend of maximum SST near zero, but this signal is not robust – by using different data or periods the signal disappears. We do find a negative correlation between the average warmest month for the years 1950–1969 (average SST max) and the linear trend of maximum monthly temperatures for the years 1950–2006 (linear trend SST max). However this correlation is not unique to the WPWP, it is also observed in a cooler region. Consequently it can not be explained by a thermostat. The observed sparsity of bleaching observations in the WPWP is not in agreement with estimated bleaching likelihood. The sparsity of observations is more likely due to the WPWP's remoteness.
2009-03-21T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/easpubs/8
info:doi/10.1029/2008GL036288
https://docs.lib.purdue.edu/context/easpubs/article/1004/viewcontent/Hooidonk.pdf
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Coral Bleaching
Ocean Thermostat
Western Pacific Warm Pool
oai:docs.lib.purdue.edu:easpubs-1007
2012-02-27T18:10:25Z
publication:eas
publication:easpubs
publication:sci
Global warming, convective threshold and false thermostats
Williams, I. N.
Pierrehumbert, R. T.
Huber, M.
2009-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/easpubs/5
https://docs.lib.purdue.edu/context/easpubs/article/1007/viewcontent/Williams.pdf
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1006
2012-02-27T18:06:52Z
publication:eas
publication:easpubs
publication:sci
Global methane emissions from wetlands, rice paddies, and lakes
Zhuang, Q..
Melack, J. M.
Zimov, S.
Walter, K. M.
Butenhoff, C. L.
Khalil, M. A.K.
2009-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/easpubs/6
https://docs.lib.purdue.edu/context/easpubs/article/1006/viewcontent/Zhuang.pdf
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1012
2012-05-15T20:42:10Z
publication:eas
publication:easpubs
publication:sci
Transpressional rupture of an unmapped fault during the 2010 Haiti earthquake
Calais, E.
Freed, A.
Mattioli, G.
Amelung, F.
Jónsson, S.
Jansma, P.
Hong, S. H.
Dixon, T.
Prépetit, C.
Momplaisir, R.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/13
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1014
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
An Extended Solar Cycle 23 with Deep Minimum Transition to Cycle 24: Assessments and Climatic Ramifications
Agee, Ernest M.
Cornett, Emily
Gleason, Kandace
The extended length of solar cycle 23 and the associated deep quiet period (QP) between cycles 23 and 24 have been examined using the international sunspot record from 1755 to 2010. This study has also introduced a QP definition based on a (beginning and ending) mean monthly threshold value of less than 10 for the sunspot number. Features addressed are the length and intensity of cycle 23, the length of the QP and the associated number of spotless days, and the respective relationships between cycle intensity, length, and QP. The length of cycle 23 (153 months) is second only to cycle 4 (164 months), with an average of 132.5 months for the 11-yr cycle. The length of the QP between cycles 23 and 24 ranks eighth, extending from October 2005 through November 2009 (but subject to continued weakness in cycle 24). The number of spotless days achieved within this QP was 751 (and for all days within the transition from cycle 23 to cycle24, a record number of 801 spotless days had been observed through May 2010). Shortcomings of solar-convection-model predictions of sunspot activity and intensity are also noted, including the failure in the initial predictions of cycle-24 onset. The relevance of an extended quiet solar period and the potential reduction of total solar irradiance (TSI) are also discussed, both in the context of climate-model simulations of future climate change as well as with regard to future satellite measurements of TSI.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/15
info:doi/10.1175/2010JCLI3831.1
http://journals.ametsoc.org/doi/abs/10.1175/2010JCLI3831.1
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Solar cycle
Climate sensitivity
Climate change
Interdecadal variability
Model evaluation/performance
oai:docs.lib.purdue.edu:easpubs-1019
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Developing a process model for visual penetrative ability
Alles, Mathew
Riggs, Eric M.
Visual penetrative ability (VPA) is a basic skill for any geology undergraduate student and is also required in many introductory laboratory exercises designed for nonmajors. This is the ability to visualize the three-dimensional (3-D) underground structure of folded sedimentary rocks from two-dimensional (2-D) surface clues. This study seeks to understand the origins of difficulties that introductory geology students encounter with this task. Problem-solving interviews were conducted with students representing the range of performance on the GeoSAT, a semiquantitative instrument designed to measure VPA. We conducted think-aloud, discursive interviews where participants solved similar 3-D visualization tasks. The interviewers interacted with participants to probe their problem-solving difficulties and thought processes while they were working. Analysis of interviews and videotapes of student gestures yielded insight into the nature of the difficulties faced by students in solving this style of spatial problem, and explained the origin of many of the common incorrect responses seen by previous workers using the GeoSAT. Students with high VPA appear to rapidly construct a 3-D internal visual model, and readily produced gestures and physical expressions illustrating their spatial understanding. Students with poor VPA tend to view external information as merely a type of "gift wrapping" over the cubic volume and do not perceive the internal structure. They also do not typically address spatial concepts through physical expression. We construct a process model for VPA that describes the origin of commonly observed errors at crucial steps, and associated accommodation strategies used by students struggling with spatial visualization of this type.
2011-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/20
info:doi/10.1130/2011.2474(06)
http://specialpapers.gsapubs.org/content/474/63
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
block diagrams
education
geology
three-dimensional models
visual penetrative ability
oai:docs.lib.purdue.edu:easpubs-1017
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Mammalian biodiversity on Madagascar controlled by ocean currents
Ali, Jason R.
Huber, Matthew
Madagascar hosts one of the world’s most unusual, endemic, diverse and threatened concentrations of fauna1. To explain its unique, imbalanced biological diversity, G. G. Simpson proposed the ‘sweepstakes hypothesis’, according to which the ancestors of Madagascar’s present-day mammal stock rafted there from Africa2. This is an important hypothesis in biogeography and evolutionary theory for how animals colonize new frontiers1, 3, 4, 5, but its validity is questioned5, 6, 7, 8, 9. Studies suggest that currents were inconsistent with rafting to Madagascar9 and that land bridges provided the migrants’ passage5, 6, 7, 8. Here we show that currents could have transported the animals to the island and highlight evidence inconsistent with the land-bridge hypothesis. Using palaeogeographic reconstructions and palaeo-oceanographic modelling, we find that strong surface currents flowed from northeast Mozambique and Tanzania eastward towards Madagascar during the Palaeogene period, exactly as required by the ‘sweepstakes process’. Subsequently, Madagascar advanced north towards the equatorial gyre and the regional current system evolved into its modern configuration with flows westward10 from Madagascar to Africa. This may explain why no fully non-aquatic land mammals have colonized Madagascar since the arrival of the rodents and carnivorans during the early-Miocene epoch. One implication is that rafting may be the dominant means of overseas dispersal in the Cenozoic era when palaeocurrent directions are properly considered.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/18
info:doi/10.1038/nature08706
http://www.nature.com/nature/journal/v463/n7281/full/nature08706.html
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1016
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Effect of tile effluent on nutrient concentration and retention efficiency in agricultural drainage ditches
Ahiablame, L. M.
Chaubey, I.
Smith, D. R.
Engel, B. A.
Tile drainage is a common water management practice in many agricultural landscapes in the Midwestern United States. Drainage ditches regularly receive water from agricultural fields through these tile drains. This field-scale study was conducted to determine the impact of tile discharge on ambient nutrient concentration, nutrient retention and transport in drainage ditches. Grab water samples were collected during three flow regimes for the determination of soluble phosphorus (SP), ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3-N) concentrations and their retention in three drainage ditches. Measured nutrient concentration indicated lower SP and NH4+-N, and greater NO3-N concentrations in tile effluents compared to the ditch water. Net uptake lengths were relatively long, especially for NO3-N, indicating that nutrients were generally not assimilated efficiently in these drainage systems. Results also indicated that the study reaches were very dynamic showing alternating increases or decreases in nutrient concentration across the flow regimes. The drainage ditches appeared to be nutrient-rich streams that could potentially influence the quality of downstream waters. --------------------------------------------------------------------------------
2011-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/17
info:doi/10.1016/j.agwat.2011.03.002
http://www.sciencedirect.com/science/article/pii/S0378377411000527
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Net uptake length
Soluble phosphorus
Ammonium nitrogen
Downstream water quality
Agricultural land use
oai:docs.lib.purdue.edu:easpubs-1041
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Gravitational potential energy and regional stress and strain rate fields for continental plateaus: Examples from the central Andes and Colorado Plateau
Flesch, Lucy M
Kreemer, Corne
The commonly observed extension in areas of elevated and thickened crust is an expected consequence of having excess gravitational potential energy (GPE) compared to the low GPE of the surrounding crust. While this conceptual model is well founded, it is less clear how well GPE-related stress orientations compare quantitatively to observed stress and strain rate orientations and what any inconsistency tells us about the presence of other competing forces. We estimate the GPE distribution for the central Andes and the greater Colorado Plateau area using topography and crustal thickness variations, respectively, and compare the related stress fields with the World Stress Map as well as with a geodetic strain rate field (for the Colorado Plateau only). In both areas, deviatoric stresses associated with GPE variations alone cannot fully account for the observed deformation rate field. For the central Andes only a combination of deviatoric stresses associated with GPE and relative plate motions can account for the near N–S tensional stress observed in the Peruvian Andes and the margin–normal compressional stress along the eastern Cordillera and sub-Andean fold-and-thrust belt. The observed deformation field around the Colorado Plateau shows E–W extension, largely inconsistent with the deviatoric stresses associated with GPE variations except for the area east of the Rio Grande Rift. The NE–SW oriented stress observed on the southwestern Colorado Plateau is consistent with the orientations of tensional deviatoric stresses associated with GPE variations. We argue that this consistency could be haphazard; stress observations may not reflect the current state of stress due to inherited structure, or could result from the relative high strength of Colorado Plateau that allows for regional GPE variations (and possibly basal shear) to be more significant forces than far-field plate interactions. For the central Andes and Colorado Plateau, stresses associated with GPE variations have a strong influence on the total stress field, and can thus be used to calibrate the overall level of deviatoric stress acting within the lithosphere.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/42
info:doi/10.1016/j.tecto.2009.07.014
http://www.sciencedirect.com/science/article/pii/S0040195109003825
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Tectonic stress
Plate boundary deformation
Gravitational potential energy
Lithospheric dynamics
Altiplano
Colorado Plateau
oai:docs.lib.purdue.edu:easpubs-1022
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
A New Three-Dimensional Visualization System for Combining Aircraft and Radar Data and Its Application to RICO Observations
Arthur, Dan K.
Lasher-Trapp, Sonia
Abdel-Haleem, Ayman
Klosterman, Nicholas
Ebert, David S.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/23
info:doi/10.1175/2009JTECHA1395.1
http://journals.ametsoc.org/doi/abs/10.1175/2009JTECHA1395.1
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Aircraft observations
Radar observations
Data processing
Field experiments
oai:docs.lib.purdue.edu:easpubs-1013
2013-06-12T16:15:15Z
publication:eas
publication:easpubs
publication:sci
High-CO2 cloud radiative forcing feedback over both land and ocean in a global climate model
Abbot, Dorian S.
Huber, Matthew
Bousquet, Gabriel
Walker, Chris C.
A positive feedback on high-latitude winter marine climate change involving convective clouds has recently been proposed using simple models. This feedback could help explain data from equable climates, e.g., the Eocene, and might be relevant for future climate. Here this convective cloud feedback is shown to be active in an atmospheric GCM in modern configuration (CAM) at CO2 = 2240 ppm and in a coupled GCM in Eocene configuration (CCSM) at CO2 = 560 ppm. Changes in boundary conditions that increase surface temperature have a similar effect as increases in CO2 concentration. It is also found that the high-latitude winter cloud radiative forcing over land increases with increases in surface temperature due to either increased CO2 or changes in boundary conditions, which could represent an important part of the explanation for warm continental interior winter surface temperatures during equable climates. This is due to increased low-level layered clouds caused by increased relative humidity.
2009-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/easpubs/14
info:doi/10.1029/2008GL036703
https://docs.lib.purdue.edu/context/easpubs/article/1013/viewcontent/EAS_14_Matthew_Huber.pdf
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1031
2013-06-26T19:19:07Z
publication:eas
publication:easpubs
publication:sci
Spontaneous transition to superrotation in warm climates simulated by CAM3
Caballero, Rodrigo
Huber, Matthew
Recent paleoclimate proxy reconstructions show that tropical surface temperatures may have been as high as 35°–40°C in the Early Cenozoic. Here, we study the tropical atmospheric circulation's response to temperatures in this range using a full-complexity atmospheric general circulation model (AGCM). We find that when equatorial surface temperatures exceed ∼33°C, the model undergoes a transition to equatorial superrotation, a state with strong annual- and zonal-mean westerlies on the equator. The transition is driven by zonal momentum convergence due to large-amplitude transient eddies on the equator. These eddies have a structure similar to the observed Madden-Julian Oscillation (MJO). The model's MJO variability is weaker than observed when simulating the modern climate but increases sharply with temperature, coming to dominate the tropical variability and mean state of the warmest climates.
2010-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/easpubs/32
info:doi/10.1029/2010GL043468
https://docs.lib.purdue.edu/context/easpubs/article/1031/viewcontent/EAS_32_Caballero_Huber.pdf
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
superrotation
MJO
oai:docs.lib.purdue.edu:easpubs-1021
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Estimating methane emissions from northern lakes using ice-bubble surveys
Anthony, Katey W.
Vas, Drago A.
Brosius, Laura
Chapin, F. Stuart, III
Zimov, Sergey A.
Zhuang, Qianlai
The magnitude and variability in methane (CH4) emissions from lakes are uncertain due to limitations in methods for quantifying the patchiness of ebullition (bubbling). We present a field method to estimate an important and highly uncertain source: ebullition from northern lakes. We defined four classes of CH4 bubble clusters trapped in lake ice representing distinct types of biogenic ebullition seeps that differed in flux rate. Mean annual ebullition determined through long-term (up to 700 d) continuous flux measurements of 31 seeps in three Siberian and one Alaskan lake was (mean ± standard error, 4-10 seeps per class; g CH4 seep –1 y –1): A, 6 ± 4; B, 48 ± 11; C, 354 ± 52; Hotspot, 1167 ± 177. Discrete-seep ebullition comprised up to 87% of total emissions from Siberian lakes when diffusive flux and background and seep ebullition were considered together. Including seep ebullition increased previous estimates of lake CH4 emissions based on traditional methods 5- to 8-fold for Siberian and Alaskan lakes. Linking new ebullition estimates to an established biogeochemical model, the Terrestrial Ecosystem Model, increased previous estimates of regional terrestrial CH4 emissions 3- to 7-fold in Siberia. Assessment of the method revealed that ebullition seeps are an important component of the terrestrial CH4 budget. They are identifiable by seep type by independent observers; they are consistent predictors of flux rate in both Siberia and Alaska; and they allow quantification of what was previously a large source of uncertainty in upscaling CH4 emissions from lakes to regions.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/22
info:doi/10.4319/lom.2010.8.592
http://www.wap.aslo.orgwww.wap.aslo.org/lomethods/free/2010/0592.pdf
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1032
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Triggering of New Madrid seismicity by late-Pleistocene erosion
Calais, Eric
Freed, A. M.
Van Arsdale, R.
Stein, S.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/33
info:doi/10.1038/nature09258
http://www.nature.com/nature/journal/v466/n7306/full/nature09258.html#/affil-auth
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1027
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Geochemical characteristics of naturally acid and alkaline saline lakes in southern Western Australia
Bowen, Brenda Beitler.
Benison, Kathleen C.
Abundant shallow saline lakes on the Archean Yilgarn Craton in southern Western Australia exhibit a rare spectrum of geochemical conditions. Here the field geochemistry over three seasons (pH, salinity, and temperature), as well as major ions, trace elements, and H, O, and S stable isotopes of surface waters and shallow groundwaters from 59 ephemeral lakes in southern Western Australia (WA) are reported. Approximately 40% of the lakes and 84% of the measured groundwaters in WA are extremely acidic (pH < 4) and pHs are observed as low as 1.7. The salinity of lake waters and groundwaters ranges from rare freshwaters to common saline waters and brines with total dissolved solids >28%. The fluids are typically Na–Cl to Na–Mg–Cl–SO4 brines with variable yet locally high amounts of Ca, K, Al, Fe, Si, and Br. The acid brine fluid compositions are unusual. For example, in some fluids the amount of Al≫Ca, the amount of Br > K, and comparison of total S to
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/28
info:doi/10.1016/j.apgeochem.2008.11.013
http://www.sciencedirect.com/science/article/pii/S0883292708004034
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1026
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Milankovitch and sub-Milankovitch forcing of the Oxfordian (Late Jurassic) Terres Noires Formation (SE France) and global implications
Boulila, S.
Galbrun, B.
Hinnov, L. A.
Collin, P. Y.
Ogg, James G.
Fortwengler, D.
Marchand, D.
High-resolution analysis (2277 samples) of magnetic susceptibility (MS) was performed on ∼700-m-thick Early–Middle Oxfordian marine marls of the Terres Noires Formation, SE France. MS variations within these sediments record sub-Milankovitch to Milankovitch frequencies with long-term eccentricity (405 kyr and ∼2 Myr) being the most prominent. The 405 kyr cycle was used as a high-resolution geochronometer for astronomical calibration of this poorly constrained interval of Late Jurassic time. The estimated duration of this Early–Middle Oxfordian interval concurs with the current International Geologic Time Scale GTS2004 (∼4 Myr), but the estimated durations of the corresponding ammonite zones are notably different. The calibration improves the resolution and accuracy of the M-sequence magnetic anomaly block model that was previously used to establish the Oxfordian time scale. Additionally, the 405 kyr cyclicity is linked to third-order sea-level depositional sequences observed for Early–Middle Oxfordian time. Strong ∼2 Myr cycles are consistent with long-term eccentricity modulation predicted for the Late Jurassic. These cycles do not match second-order sequences that have been documented for European basins; this raises questions about the definition and hierarchy of depositional sequences in the Mesozoic eustatic chart. Our results require substantial revisions to the chart, which is frequently used as a reference for the correlation of widely separated palaeogeographic domains. Finally, a long-term trend in the MS data reflects a progressive carbonate enrichment of the marls expressing an Early Oxfordian global cooling followed gradually by a warming in the Middle Oxfordian. This trend also records a major transgressive interval likely peaking at the Transversarium ammonite zone of the Middle Oxfordian.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/27
info:doi/10.1111/j.1365-2117.2009.00429.x
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2117.2009.00429.x/abstract;jsessionid=37C46E537B87716D1EFBAD6100C12F37.d03t04?systemMessage=Wiley+Online+Library+will+be+disrupted+on+9+June+from+10%3A00-12%3A00+BST+%2805%3A00-07%3A00+EDT%29+for+essential+maintenance
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1025
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Imaging spectroscopy of jarosite cement in the Jurassic Navajo Sandstone
Bell, Julianne H.
Bowen, Brenda Beitler
Martini, Brigette A.
Imaging spectroscopy is a powerful tool for mapping surface mineralogy. Interactions of energy and surface materials on atomic and molecular levels result in specific absorption features that are diagnostic of mineralogy. Hyperspectral airborne sensors such as HyMap have sufficient spectral resolution to identify subtle features over narrow wavelength ranges. An anomalous zone of jarosite cement within the Jurassic Navajo Sandstone in southern Utah was identified with airborne hyperspectral data. To date no other locations of sulfate-rich cements such as this have been documented in the Navajo Sandstone. Here, we use multiple spectral analysis techniques over a micro to macro spatial continuum in order to focus our evaluation on the distribution and relative abundance of jarosite in this area. In this study, imaging spectroscopy is used to help determine the extent of the distribution of jarosite [KFe3(SO4)2(OH)6], at “Mollie's Nipple” (MN), a significant geomorphic landmark located within the Grand Staircase-Escalante National Monument, in the Jurassic Navajo Sandstone of south central Utah. The extent of the jarosite across the butte is identified in this study by mapping two diagnostic absorption features, referred to as the ∼ 2.26 μm and near-infrared ferric iron absorption features (∼ 0.70–1.15 μm), independently. This analysis shows that there is a single circular zone of abundant jarosite ∼ 1 km in diameter that includes both in-situ and weathered out accumulations. Jarosite formation requires acidic and sulfate-rich fluids, which are unusual for the Navajo Sandstone. Imaging and field spectroscopy provides the spectral resolution needed to map and analyze the mineralogic characteristics of this area; characteristics that may help constrain the conditions under which this atypical butte formed.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/26
info:doi/10.1016/j.rse.2010.05.002
http://www.sciencedirect.com/science/article/pii/S0034425710001422
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Imaging spectroscopy
Jarosite
Hyperspectral
Geology
oai:docs.lib.purdue.edu:easpubs-1040
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Analytic continuation of eigenvalues of a quartic oscillator
Eremenko, Alexandre
Gabrielov, Andrei
We consider the Schrödinger operator on the real line with even quartic potential x4 + α x2 and study analytic continuation of eigenvalues, as functions of parameter α. We prove several properties of this analytic continuation conjectured by Bender, Wu, Loeffel and Martin. 1. All eigenvalues are given by branches of two multi-valued analytic functions, one for even eigenfunctions and one for odd ones. 2. The only singularities of these multi-valued functions in the complex α-plane are algebraic ramification points, and there are only finitely many singularities over each compact subset of the α-plane. [ABSTRACT FROM AUTHOR].
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/41
info:doi/10.1007/s00220-008-0663-6
http://web.ebscohost.com/ehost/detail?sid=4e44a5e7-fb56-4414-a561-41148d27d1ec%40sessionmgr4&vid=1&hid=24&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=mth&AN=36649764
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
EIGENVALUES
MATRICES
NONLINEAR oscillators
oai:docs.lib.purdue.edu:easpubs-1044
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Could Pantheon Fossae be the result of the Apollodorus crater-forming impact within the Caloris basin, Mercury?
Freed, Andrew M.
Solomon, Sean C.
Watters, Thomas R.
Phillips, Roger J.
Zuber, Maria T.
The ~ 40-km-diameter Apollodorus impact crater lies near the center of Pantheon Fossae, a complex of radiating linear troughs itself at the approximate center of the 1500-km-diameter Caloris basin on Mercury. Here we use a series of finite element models to explore the idea that the Apollodorus crater-forming impact induced the formation of radially oriented graben by altering a pre-existing extensional stress state. Graben in the outer portions of the Caloris basin, which display predominantly circumferential orientations, have been taken as evidence that the basin interior was in a state of horizontal extensional stress as a result of uplift. If the Apollodorus crater formed at the time of such a stress state, impact-induced damage to basin fill material would have caused basin material to move radially outward, leading to a decrease in the radial extensional stress and an increase in the circumferential stress. If this change in differential stress was sufficient to induce failure, the predicted style of faulting would be radial graben extending outward from the exterior crater rim. The ~ 230-km radial extent of Pantheon Fossae implies, by this scenario, that the Apollodorus impact generated a large damage zone, extending to perhaps three crater radii (~ 60 km) or more. The calculations also suggest, under this scenario, that the Caloris basin fill had greater strength than the surrounding crust and that the basin uplift and extensional stress field prior to the Apollodorus impact were close to azimuthally symmetric. The location of Pantheon Fossae very near the center of the Caloris basin appears to be coincidental; any crater similar in size to Apollodorus and located within ~ 300 km of the basin center could have produced a radiating set of graben by the mechanism explored here.
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/45
info:doi/10.1016/j.epsl.2009.02.038
http://www.sciencedirect.com/science/article/pii/S0012821X09001368
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Mercury
Caloris basin
Pantheon Fossae
Apollodorus crater
oai:docs.lib.purdue.edu:easpubs-1038
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
New paleomagnetic and stable-isotope results from the Nanxiong Basin, China: Implications for the K/T boundary and the timing of Paleocene mammalian turnover
Clyde, William C.
Ting, Suyin
Snell, Kathryn E.
Bowen, Gabriel J.
Tong, Yongsheng
Koch, Paul L.
Li, Quan
Wang, Yuanqing
The Nanxiong Basin (Guangdong Province, China) preserves the most complete Asian stratigraphic record of the Cretaceous-Paleogene (K/Pg) boundary extinction and the subsequent Paleocene mammalian radiation. Despite extensive study, the precise placement of the K/Pg boundary in the Nanxiong Basin sequence has been controversial, and the timing of subsequent mammalian turnover is poorly constrained. We present new paleomagnetic and geochemical data from the Late Cretaceous Pingling Formation (Nanxiong Group) and the overlying Paleocene Shanghu, Nongshan, and Guchengcun formations (Luofozhai Group). Our samples are directly correlated with previous geochemical and paleontological sampling localities, allowing for easy comparison with other local proxy records. Results indicate that the traditional placement of the K/Pg boundary at the base of a chaotic channel sandstone bed marking the highest stratigraphic appearance of dinosaur eggshell fragments and lowest stratigraphic appearance of Paleocene mammalian fossils lies about two-thirds of the way up Chron C29R, consistent with the placement of the boundary in all other well-documented sections. The average carbon isotope composition of paleosol carbonates decreases by 12‰ in the Early Paleocene, consistent with a major disruption to global carbon cycling after the K/Pg boundary. Constraints on the age of the first major Cenozoic mammalian turnover event in Asia (the Shanghuan-Nongshanian Asian Land Mammal Age boundary) support its placement near the top of Chron C27N, which coincides with a similar turnover in North America and geochemical changes recorded in several deep sea cores. [ABSTRACT FROM AUTHOR]
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/39
info:doi/10.1086/649893
http://web.ebscohost.com/ehost/detail?sid=6fa01e7b-de4c-4529-ba9b-e67ca5368aa9%40sessionmgr15&vid=1&hid=24&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=aph&AN=47790975
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Paleomagnetism
geochemistry
sandstone
goelogy
oai:docs.lib.purdue.edu:easpubs-1029
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Dietary and physiological controls on the hydrogen and oxygen isotope ratios of hair from mid-20th century indigenous populations
Bowen, Gabriel J.
Ehleringer, James R.
Chesson, Lesley A.
Thompson, Alexandra H.
Podlesak, David W.
Cerling, Thure E.
A semimechanistic model has recently been proposed to explain observed correlations between the H and O isotopic composition of hair from modern residents of the USA and the isotopic composition of drinking water, but the applicability of this model to hair from non-USA and preglobalization populations is unknown. Here we test the model against data from hair samples collected during the 1930s–1950s from populations of five continents. Although C and N isotopes confirm that the samples represent a much larger range of dietary “space” than the modern USA residents, the model is able to reproduce the observed δ2H and δ18O values given reasonable adjustments to 2 model parameters: the fraction of dietary intake derived from locally produced foods and the fraction of keratin H fixed during the in vivo synthesis of amino acids. The model is most sensitive to the local dietary intake, which appears to constitute between 60% and 80% of diet among the groups sampled. The isotopic data are consistent with a trophic-level effect on protein H isotopes, which we suggest primarily reflects mixing of 2H-enriched water and 2H-depleted food H in the body rather than fractionation during biosynthesis. Samples from Inuit groups suggest that humans with marine-dominated diets can be identified on the basis of coupled δ2H and δ18O values of hair. These results indicate a dual role for H and O isotopic measurements of keratin, including both biological (diet, physiology) and environmental (geographic movement, paleoclimate) reconstruction. Am J Phys Anthropol, 2009. © 2009 Wiley-Liss, Inc.
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/30
info:doi/10.1002/ajpa.21008
http://onlinelibrary.wiley.com/doi/10.1002/ajpa.21008/abstract;jsessionid=CD181A50164AE7D4C1C9669D1C62F0E1.d04t03?systemMessage=Wiley+Online+Library+will+be+disrupted+on+9+June+from+10%3A00-12%3A00+BST+%2805%3A00-07%3A00+EDT%29+for+essential+maintenance
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
stable isotopes
keratin
model
oai:docs.lib.purdue.edu:easpubs-1037
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Do Earth anD EnvironmEntal SciEncE tExtbookS PromotE miDDlE anD high School StuDEntS’concEPtual DEvEloPmEnt about climatE changE?
Choi, Soyoung
Niyogi, Dev
Shepardson, Daniel P.
Charusombat, Umarporn
Misconceptions or a lack of relevant prior concepts can hinder students from developing an understanding of scientific concepts. Science education research suggests that building on students' prior concepts is an effective way to develop students' scientific knowledge. This study reports the results of an analysis of earth and environmental science textbooks' representations of climate change concepts and an examination of these presentations for possible contribution to students' common misconceptions of climate change. A literature review was conducted to identify students' common misconceptions of climate change. Textbooks' conceptual coverage and their ways of presenting scientific conceptions were examined concerning their potential influence on further reinforcing and adding greater confidence to students' misconceptions. Our results indicate that the reviewed textbooks were not designed based on careful consideration of students' common misconceptions of climate change. We made recommendations for improving the conceptual clarity and organization of climate change concepts in Earth and environmental science textbooks.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/38
info:doi/10.1175/2009BAMS2625.1
http://journals.ametsoc.org/doi/abs/10.1175/2009BAMS2625.1
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1024
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Some lower bounds in the B. and M. Shapiro conjecture for flag varieties
Azar, Monique
Gabrielov, Andrei
2011-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/25
info:doi/10.1007/s00454-010-9314-8
http://dl.acm.org/citation.cfm?id=2134333
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1042
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Improved imaging with phase-weighted common conversion point stacks of receiver functions
Frassetto, A.
Zandt, G.
Gilbert, H.
Owens, T. J.
Jones, C. H.
Broad-band array studies frequently stack receiver functions to improve their signal-to-noise ratio while mapping structures in the crust and upper mantle. Noise may produce spurious secondary arrivals that obscure or mimic arrivals produced by P-to-S conversions at large contrasts in seismic impedance such as the Moho. We use a Hilbert transform to calculate phase-weights, which minimize the constructive stacking of erroneous signal in receiver function data sets. We outline this approach and demonstrate its application through synthetic data combined with different types of noise, a previously published example of signal-generated noise, and a large data set from the Sierra Nevada EarthScope Project. These examples show that phase-weighting reduces the presence of signal-generated noise in receiver functions and improves stacked data sets.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/43
info:doi/10.1111/j.1365-246X.2010.04617.x
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-246X.2010.04617.x/abstract
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Image processing
Interface waves
Site effects
Wave scattering and diffraction
Crustal structure
oai:docs.lib.purdue.edu:easpubs-1036
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Differentiating impacts of land use changes from pasture management in a CEAP watershed using SWAT model
Chiang, Li-Chi
Chaubey, Indrajeet
Gitau, Margaret W
Arnold, Jeffrey G
Due to intensive farm practices, nonpoint-source (NPS) pollution has become one of the most challenging environmental problems in agricultural and mixed land use watersheds. Usually, various conservation practices are implemented in the watershed to control the NPS pollution problem. However, land use changes can mask the water quality improvements from the conservation practices implemented in the watershed. The objectives of this study were to evaluate the linkage between nutrient input from various pasture management practices and water quality, and to quantify the impacts of land use changes and pasture management on water quality in a pasture-dominated watershed. Land use data from 1992, 1994, 1996, 1999, 2001, and 2004 were evaluated for the land use changes in the watershed, and the corresponding implemented management practices were also incorporated into the Soil and Water Assessment Tool (SWAT) model. The individual impacts of land use change and pasture management were quantified by comparing the SWAT simulation results for different land use change and pasture management scenarios. The results indicated that land use changes resulted in greater total sediment (499 kg ha -1 ) and nitrogen losses (3.8 kg ha -1 ) in the Moores Creek subwatershed, whereas pasture management resulted in greater total nitrogen losses (4.3 kg ha -1 ) in the Beatty Branch subwatershed. Overall, the combined impacts of land use changes and pasture management resulted in greater total sediment (28 to 764 kg ha -1 of cumulative combined impacts between 1992 and 2007) and nitrogen losses (5.1 to 6.1 kg ha -1 ) and less total phosphorus losses (1.5 to 2.1 kg ha -1 ) in the Beatty Branch, Upper Moores Creek, and Moores Creek subwatersheds. By quantifying the individual impacts of land use changes and pasture management, we found that an increase in total nitrogen losses in the Beatty Branch subwatershed was mainly due to an increase in nutrient inputs in the pasture areas, and total sediment and nitrogen losses in the Moores Creek subwatershed were mainly due to an increase in urban lands. Therefore, the individual impacts of land use changes and conservation practices should be quantified to get a true picture of the success of CEAP programs in watersheds experiencing significant land use changes.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/37
https://elibrary.asabe.org/azdez.asp?JID=3&AID=34901&CID=t2010&v=53&i=5&T=1&redirType=
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Conservation Effects Assessment Project (CEAP)
Land use changes
Pasture management
SWAT model
oai:docs.lib.purdue.edu:easpubs-1039
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Increased seasonality through the Eocene to Oligocene transition in northern high latitudes
Eldrett, James S.
Greenwood, David R.
Harding, Ian C.
Huber, Matthew
A profound global climate shift took place at the Eocene–Oligocene transition (33.5 million years ago) when Cretaceous/early Palaeogene greenhouse conditions gave way to icehouse conditions1, 2, 3. During this interval, changes in the Earth's orbit and a long-term drop in atmospheric carbon dioxide concentrations4, 5, 6 resulted in both the growth of Antarctic ice sheets to approximately their modern size2, 3 and the appearance of Northern Hemisphere glacial ice7, 8. However, palaeoclimatic studies of this interval are contradictory: although some analyses indicate no major climatic changes9, 10, others imply cooler temperatures11, increased seasonality12, 13 and/or aridity12, 13, 14, 15. Climatic conditions in high northern latitudes over this interval are particularly poorly known. Here we present northern high-latitude terrestrial climate estimates for the Eocene to Oligocene interval, based on bioclimatic analysis of terrestrially derived spore and pollen assemblages preserved in marine sediments from the Norwegian–Greenland Sea. Our data indicate a cooling of 5 °C in cold-month (winter) mean temperatures to 0–2 °C, and a concomitant increased seasonality before the Oi-1 glaciation event. These data indicate that a cooling component is indeed incorporated in the 18O isotope shift across the Eocene–Oligocene transition. However, the relatively warm summer temperatures at that time mean that continental ice on East Greenland was probably restricted to alpine outlet glaciers.
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/40
info:doi/10.1038/nature08069
http://www.nature.com/nature/journal/v459/n7249/full/nature08069.html#abs
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1023
2013-06-12T16:19:39Z
publication:eas
publication:easpubs
publication:sci
Suppression of south Asian summer monsoon precipitation in the 21st century
Ashfaq, Moetasim
Shi, Ying
Tung, Wen-wen
Trapp, Robert J.
Gao, Xueijie
Pal, Jeremy S.
Diffenbaugh, Noah S.
We used a high-resolution nested climate modeling system to investigate the response of South Asian summer monsoon dynamics to anthropogenic increases in greenhouse gas concentrations. The simulated dynamical features of the summer monsoon compared well with reanalysis data and observations. Further, we found that enhanced greenhouse forcing resulted in overall suppression of summer precipitation, a delay in monsoon onset, and an increase in the occurrence of monsoon break periods. Weakening of the large-scale monsoon flow and suppression of the dominant intraseasonal oscillatory modes were instrumental in the overall weakening of the South Asian summer monsoon. Such changes in monsoon dynamics could have substantial impacts by decreasing summer precipitation in key areas of South Asia.
2009-01-03T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/easpubs/24
info:doi/10.1029/2008GL036500
https://docs.lib.purdue.edu/context/easpubs/article/1023/viewcontent/EAS_24_Robert_J._Trapp.pdf
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
regional climate change
south Asian monsoon
oai:docs.lib.purdue.edu:easpubs-1047
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
A computationally efficient inverse modelling approach of inherent optical properties for a remote sensing model
Garg, Vijay
Chaubey, Indrajeet
Inverse modelling of inherent optical properties (IOP) is an alternative to the in situ measurements of IOP requiring specialized instruments. However, inverse modelling using Monte Carlo models may require very large computational time due to a large number of dynamic model runs needed to search the optimum parameter values. We present a new approach to reduce this computational time. Mathematical relationships were developed for wavelength and concentration dependence of IOP values of suspended mineral based on four parameters. Optimal values of these four parameters were calculated by minimizing the mean sum of error between the physical hyperspectral optical-Monte Carlo (PHO-MC) model predicted reflectance to measured reflectance values for selected 33 reflectance measurements for a set of 11 wavelengths and three suspended sediment concentrations. The computation time was significantly reduced by several orders of magnitude by: (1) replacing the PHO-MC model with 11 wavelengths specific pseudo-simulator models developed by applying artificial neural network approach; and (2) using a nondominated sorted genetic algorithm –II (NSGA II) to search the global optimal solution of four parameters of IOP equations. Determined IOP values of suspended minerals were then successfully validated by using them as input to PHO-MC model to predict reflectance values for an independent set of 287 combinations of 41 wavelengths and seven suspended sediment concentrations.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/48
info:doi/10.1080/01431160903258225
http://www.tandfonline.com/doi/abs/10.1080/01431160903258225
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1046
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Inverse Modeling of Beaver Reservoir's Water Spectral Reflectance
Garg, Vijay
Bajwa, Sreekala G.
Chaubey, Indrajeet
Maringanti, Chetan
Estimation of inherent optical properties (IOP) needed for water quality evaluation by remote sensing models is very complex, primarily due to the large number of model simulations needed to find optimal parameter values. This study presents an approach for optimally parameterizing the IOP values of a physical hyperspectral optical - Monte Carlo (PHO-MC) model. An artificial neural network (ANN) based pseudo simulator combined with the Nondominated Sorted Genetic Algorithm II (NSGA II) was used to efficiently perform a large number of model simulations and to search the optimal parameter values for IOP determination. Concentrations of suspended matter (sm), chlorophyll-a (chl), and total dissolved organic matter (DOM) along with the reflectance data at 16 different wavelengths were measured at 48 sampling stations in the Beaver Reservoir, Arkansas, between 2003 and 2005 and were used to evaluate the IOP values. Measured concentrations and reflectance data from 24 sampling stations were used to optimize IOP parameter values for sm, chl, and DOM. The data collected from the remaining 24 sampling stations were used for the validation of PHO-MC model-predicted reflectance by using optimized IOP values. PHO-MC predicted reflectance values were significantly correlated (r = 0.90, p < 0.01) with the corresponding measured reflectance values, indicating that the pseudo simulator combined with the NSGA II accurately estimated the IOP values. An estimated 10 10 years of calculation time was reduced to less than 3 min by using the pseudo simulator and NSGA II to supplement the PHO-MC model for estimating the IOP values.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/47
https://elibrary.asabe.org/toc_journals.asp?orgconf=t2010&volume=53&conf=t&issue=2
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
ANN
Beaver Reservoir
GA
Inherent optical properties
Inverse modeling
Remote sensing
Water quality
oai:docs.lib.purdue.edu:easpubs-1048
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Contribution of gravitational potential energy differences to the global stress field
Ghosh, Attreyee
Holt, William E.
Flesch, Lucy M.
Modelling the lithospheric stress field has proved to be an efficient means of determining the role of lithospheric versus sublithospheric buoyancies and also of constraining the driving forces behind plate tectonics. Both these sources of buoyancies are important in generating the lithospheric stress field. However, these sources and the contribution that they make are dependent on a number of variables, such as the role of lateral strength variation in the lithosphere, the reference level for computing the gravitational potential energy per unit area (GPE) of the lithosphere, and even the definition of deviatoric stress. For the mantle contribution, much depends on the mantle convection model, including the role of lateral and radial viscosity variations, the spatial distribution of density buoyancies, and the resolution of the convection model. GPE differences are influenced by both lithosphere density buoyancies and by radial basal tractions that produce dynamic topography. The global lithospheric stress field can thus be divided into (1) stresses associated with GPE differences (including the contribution from radial basal tractions) and (2) stresses associated with the contribution of horizontal basal tractions. In this paper, we investigate only the contribution of GPE differences, both with and without the inferred contribution of radial basal tractions. We use the Crust 2.0 model to compute GPE values and show that these GPE differences are not sufficient alone to match all the directions and relative magnitudes of principal strain rate axes, as inferred from the comparison of our depth integrated deviatoric stress tensor field with the velocity gradient tensor field within the Earth's plate boundary zones. We argue that GPE differences calibrate the absolute magnitudes of depth integrated deviatoric stresses within the lithosphere; shortcomings of this contribution in matching the stress indicators within the plate boundary zones can be corrected by considering the contribution from horizontal tractions associated with density buoyancy driven mantle convection. Deviatoric stress magnitudes arising from GPE differences are in the range of 1–4 TN m−1, a part of which is contributed by dynamic topography. The EGM96 geoid data set is also used as a rough proxy for GPE values in the lithosphere. However, GPE differences from the geoid fail to yield depth integrated deviatoric stresses that can provide a good match to the deformation indicators. GPE values inferred from the geoid have significant shortcomings when used on a global scale due to the role of dynamically support of topography. Another important factor in estimating the depth integrated deviatoric stresses is the use of the correct level of reference in calculating GPE. We also elucidate the importance of understanding the reference pressure for calculating deviatoric stress and show that overestimates of deviatoric stress may result from either simplified 2-D approximations of the thin sheet equations or the assumption that the mean stress is equal to the vertical stress.
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/49
info:doi/10.1111/j.1365-246X.2009.04326.x
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-246X.2009.04326.x/full
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Continental margins: convergent
Continental margins: divergent
Continental margins: transform
Dynamics of lithosphere and mantle
Dynamics: gravity and tectonics
Neotectonics
oai:docs.lib.purdue.edu:easpubs-1033
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
A Proposed Model-Based Methodology for Feature-Specific Prediction for High-Impact Weather
Carley, Jacob R.
Schwedler, Benjamin R.J.
Baldwin, Michael E.
Trapp, Robert J.
Kwiatkowski, John
Logsdon, Jeffrey
Weiss, Steven J.
A feature-specific forecasting method for high-impact weather events that takes advantage of high-resolution numerical weather prediction models and spatial forecast verification methodology is proposed. An application of this method to the prediction of a severe convective storm event is given.
2011-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/34
info:doi/10.1175/WAF-D-10-05008.1
http://journals.ametsoc.org/doi/abs/10.1175/WAF-D-10-05008.1
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1015
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Nutrient Content at the Sediment-Water Interface of Tile-Fed Agricultural Drainage Ditches
Ahiablame, Laurent
Chaubey, Indrajeet
Smith, Douglas
Extensive network of tile drains present in the Midwest USA accelerate losses of nutrients to receiving ditches, rivers and eventually to the Gulf of Mexico. Nutrient inputs from agricultural watersheds and their role in affecting water quality have received increased attention recently; however, benthic sediment-nutrient interactions in tile-fed drainage ditches is still a matter of active research in consideration to nutrient discharge from tile drains. In this study, phosphorus (P) and nitrogen (N) contents and variability of nutrient retention ability of benthic sediments upstream and downstream from tile drain outlets were evaluated in managed agricultural drainage ditches in Indiana. Sediment samples were collected every three months upstream and downstream from selected tile drains in three ditches in northwest Indiana. Sediment equilibrium P concentrations (EPC0) were measured to examine P adsorption-desorption and equilibrium characteristics of benthic sediments in the ditches. P sorption index (PSI), exchangeable P (ExP), and exchangeable NH4+-N (ExN) were measured to evaluate nutrient retention ability and readily available nutrient content of benthic sediments. Results indicated a dynamic interaction between benthic sediment and overlying water column where sediments were acting as a sink or a source of P. There were no differences in nutrient retention ability between sediments collected upstream and sediments collected downstream from the selected tile drains. While the data, except for ExN, was comparable to reported values by previous studies in Indiana’s drainage ditches, there was no particular seasonal pattern in the content of exchangeable nutrient content in sediments at all three sites. This study also suggested that nutrient uptake by benthic sediments in these drainage ditches is not always efficient; therefore watershed management should focus on minimizing the delivery of nutrients into ditches while maintaining their drainage functionality.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/16
info:doi/10.3390/w2030411
http://www.mdpi.com/2073-4441/2/3/411
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
sediments
EPC0
nutrient dynamics
sediment interactions
drainage ditches
oai:docs.lib.purdue.edu:easpubs-1018
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Contemporary deformation and stressing rates in Southern Alaska
Ali, Syed Tabrez
Freed, Andrew M.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/19
info:doi/10.1111/j.1365-246X.2010.04784.x
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-246X.2010.04784.x/abstract;jsessionid=4D9B3FC7AA1C5A3907F7AD9CEDB4053D.d02t04?systemMessage=Wiley+Online+Library+will+be+disrupted+on+9+June+from+10%3A00-12%3A00+BST+%2805%3A00-07%3A00+EDT%29+for+essential+maintenance
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Seismic cycle
Transient deformation
Earthquake interaction
forecasting
and prediction
Continental margins: convergent
Rheology: crust and lithosphere
oai:docs.lib.purdue.edu:easpubs-1020
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Flat-slab subduction and crustal models for the seismically active Sierras Pampeanas region of Argentina
Alvarado, Patricia
Pardo, Mario
Gilbert, Hersh
Miranda, Silvia
Anderson, Megan
Saez, Mauro
Beck, Susan
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/21
info:doi/10.1130/2009.1204(12)
http://memoirs.gsapubs.org/content/204/261#aff-1
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1028
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Isoscapes: Spatial Pattern in Isotopic Biogeochemistry
Bowen, Gabriel J.
Isotope ratios of actively cycled elements vary as a function of the biogeochemical processes in which they participate and the conditions under which those processes occur. The resultant spatiotemporal distribution of isotopes in environmental materials can be predicted using models of isotope-fractionating processes and data describing environmental conditions across space and time, and it has been termed an isoscape, or isotopic landscape. Analysis of isoscapes and comparison of isoscape predictions with observational data have been used to test biogeochemical models, calculate aerially integrated biogeochemical fluxes based on isotope mass balance, and determine spatial connectivity in biogeochemical, ecological, and anthropological systems. Isoscape models of varying quality are available for stable H, C, N, and O isotopes in a range of Earth surface systems, but significant opportunities exist to refine our understanding of biogeochemical cycles and our ability to predict isoscapes through the development of more mechanistic and more comprehensive isoscape models.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/29
info:doi/10.1146/annurev-earth-040809-152429
http://www.annualreviews.org/doi/abs/10.1146/annurev-earth-040809-152429
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1034
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Effectiveness of best management practices in improving water quality in a pasture-dominated watershed
Chaubey, Indrajeet
Chiang, Lichi
Gitau, Margaret W.
Mohamed, Sayeed
The nonpoint source pollution problem can be controlled by implementing various best management practices (BMPs) in the watershed. However, before such practices are adopted, their effectiveness at various spatial and temporal scales must be evaluated. The objective of this research was to evaluate a suite of BMPs in a pasture-dominated watershed in their effectiveness at controlling nutrient losses. A total of 171 different BMP combinations incorporating grazing and pasture management, riparian and buffer zones, and poultry litter applications were evaluated for their effectiveness using the Soil and Water Assessment Tool (SWAT) model. The SWAT model was parameterized using detailed farm and watershed-scale data. The stochasticity in weather was captured by generating 250 various possible weather realizations for a 25-year period, using measured historical climate data for the watershed. Model results indicated that losses of both total nitrogen, mineral phosphorus, and total phosphorus increased with an increase in litter application rates. For the same application rates, greatest losses were predicted for fall application timings compared to spring and summer applications. Overgrazing resulted in greater nutrient losses compared to baseline conditions for all application rates, timings, and litter characteristics, indicating that overgrazing of pasture areas must be avoided if any improvement in the water quality is to be expected. Variability in weather conditions significantly affected BMP performance; under certain weather conditions, an increase in pollutant losses can be greater than reductions due to BMPs implemented in the watershed. Buffer strips and grazing management were two most important BMPs affecting the losses of total nitrogen and total phosphorus from the pasture areas.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/35
info:doi/10.2489/jswc.65.6.424
http://www.jswconline.org/content/65/6/424
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1035
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Shear-wave birefringence and current configuration of converging lithosphere under Tibet
Chen, Wang-Ping
Martin, Michael
Tseng, Tai-Lin
Nowack, Robert L.
Hung, Shu-Huei
Huang, Bor-Shouh
New data from west-central Tibet show that birefringence of S-waves has two pronounced increases in magnitude toward the hinterland. Null birefringence persists to about 75 km north of the Indus–Yarlung suture (IYS) between the Indian shield and the Lhasa terrane of southern Tibet. A second, rapid increase occurs about 100 km farther north of the Bangong–Nujiang sutures between the Lhasa terrane and the Qiangtang terrane in central Tibet. The latter feature is consistently observed along three long transects that collectively span a lateral (orogen-parallel) distance of about 600 km and is likely to mark the northern, leading edge of sub-horizontally advancing mantle lithosphere of the Indian shield (the “Greater India”) — an interpretation consistent with the latest results of finite-frequency tomography using both P- and S-wave travel-times, previous results of modeling gravity anomalies, and a host of other seismic observations. Similarly, complementary constraints indicate that the sudden onset of significant birefringence north of the IYS is likely to be the southern termination of Eurasian mantle lithosphere. Curiously, the shortest of three transects showed null birefringence through much of the Lhasa terrane, a pattern inconsistent with those of He isotopes and gravity.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/36
info:doi/10.1016/j.epsl.2010.04.017,
http://www.sciencedirect.com/science/article/pii/S0012821X10002554
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
seismic anisotropy
collision zone
continental lithosphere
Tibet-Himalayas
Hi-CLIMB
--------------------------------------------------------------------------------
oai:docs.lib.purdue.edu:easpubs-1043
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Steady-state laboratory flow laws alone fail to explain postseismic observations
Freed, Andrew M.
Herring, Thomas
Bürgmann, Roland
We test whether laboratory derived steady-state flow laws for wet olivine can be used to explain postseismic relaxation in the upper mantle following the 1999 Hector Mine earthquake. This is accomplished using rate changes in GPS observed displacement time-series at far-field stations as constraints on the parameters associated with laboratory derived temperature- and stress-dependent flow laws for diffusion and dislocation creep of olivine. We primarily concentrate on the influences of temperature, grain size, and background strain rate to explain observed fast early displacement rates that slow rapidly in the 7 years of postseismic observations. We find that a reasonable fit to the observed time-series cannot be achieved by any combination of flow law parameters and plausible assumptions for the tectonic environment of the mantle beneath the Mojave Desert. We conclude that postseismic relaxation within the mantle following the Hector Mine earthquake likely includes an initial transient weakening phase, suggesting that steady-state flow laws by themselves are insufficient to characterize the flow of mantle rocks when stress conditions evolve.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/44
info:doi/10.1016/j.epsl.2010.10.005
http://www.sciencedirect.com/science/article/pii/S0012821X10006394
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
postseismic relaxation
rheology
Hector Mine
dislocation creep
geodesy
finite element modeling
oai:docs.lib.purdue.edu:easpubs-1045
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Density profiles of oceanic slabs and surrounding mantle: integrated thermodynamic and thermal modeling, and implications for the fate of slabs at the 660 km discontinuity
Ganguly, Jibamitra
Freed, Andrew M.
Saxena, Surendra K.
We have calculated the mineralogical properties of the Earth's mantle and the lithological units constituting the subducting oceanic slabs within a wide range of P–T conditions within the CaO–FeO–MgO–Al2O3–SiO2 system, except for the basalt top-layer of a slab, for which the system is extended to include Na2O. The mineralogical data are then converted, using the appropriate P–V–T relations, to bulk densities. The calculated adiabatic density vs. depth profile of the mantle between 200 and 725 km depths is in good agreement with geophysical and experimental data. The density data of the different compositional units are combined with calculated thermal structures for a variety of slab–mantle systems to construct equilibrium density profiles as a function of depth. The mean equilibrium densities of the slabs within the transition zone (400–660 km depth) are found to be ∼0.04–0.05 g/cm3 greater than those of the ambient mantle within the same depth interval. For the entire upper mantle, density differences between slabs and ambient mantle are slightly less, but the slabs still remain denser than the latter. At 670 km depth, slabs have lower density than the ambient lower mantle because of the commencement of perovskite forming reactions within the mantle, and displacements of these reaction boundaries to higher pressures within the slabs as a consequence of their negative P–T slopes. If perovskite forming reactions within slabs are hindered for kinetic sluggishness, then neutral buoyancy would be achieved when the slabs have penetrated ∼100 km into the lower mantle. However, using the available data on the kinetics of spinel to perovskite plus periclase reaction, we conclude that the reaction would go to completion in a Peru-type young slab (41 Myr), and very likely also in a Tonga-type old slab (110 Myr), before these penetrated 100 km into the lower mantle. Thus, slabs should always remain negatively buoyant, and therefore continue to subduct through the lower mantle once it penetrates through the 660 km discontinuity. Despite a negative buoyancy force, a slab could deflect at the top of the lower mantle (660 km) because of factors resisting subduction, namely viscosity jump, low dip angle, slab roll back, and metastable persistence of olivine in cold slabs. If published scale model experiments represent realistic approximations of the factors affecting plate subduction, then according to our density data, any slab with a dip angle of ≤40–50° would bend at the 660 km discontinuity if there is a viscosity jump of at least by a factor of ∼10 and trench migration. The basalt top-layer of a slab is denser than other slab components and the ambient mantle at all depths to 660 km, and therefore should continue to sink into the lower mantle, especially if a slab directly penetrates the 660 km barrier, instead of peeling off in the transition zone to form a “perched eclogite” or “piclogite” layer, as previously proposed. The harzburgite layer, which is sandwiched between denser basalt and lherzolite layers, faces greater resistance to subduction, especially in a young slab, and thus could significantly contribute to the deformation of a slab near the 660 km discontinuity.
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/46
info:doi/10.1016/j.pepi.2008.10.005,
http://www.sciencedirect.com/science/article/pii/S0031920108003038
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Density
Transition zone
Mantle
Slab
Subduction
oai:docs.lib.purdue.edu:easpubs-1050
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Propagation of plasma bubbles observed in Brazil from GPS and airglow data
Haase, Jennifer S.
Dautermann, T.
Taylor, M. J.
Chapagain, N.
Calais, E.
Pautet, D.
Equatorial spread-F is a common occurrence in the equatorial ionosphere that is associated with large variations in plasma density that often cause scintillation and interference in communication signals. These events are known to result from Rayleigh–Taylor instability, but the day-to-day variability of their occurrence is not well understood. The triggering mechanism of plasma depletions is still a matter of debate, but may be linked to gravity waves that under favorable conditions propagate to the middle atmosphere. Understanding the triggering of ESF was the focus of the SpreadFEx campaign near Brasilia, Brazil in 2005. The campaign provided co-located airglow and GPS observations to study the onset of plasma depletions and their evolution as they traversed the region. Comparisons between the 630.0 nm airglow data and GPS data demonstrate the ability of the compact dual frequency GPS array to detect the plasma bubbles and retrieve reliable propagation characteristics of the depletions. In this case study, a plasma depletion was detected and moved over the array at velocities of 85–110 m/s, slowing as it moved towards the east. Correlation of consecutive airglow images gives consistent estimates of the eastward drift over the same time period. Mapping the airglow data to the GPS line-of-sight geometry allows direct comparison and reveals a resolvable westward tilt of the plasma depletion that may be due to vertical shear. The uniqueness of this study is the ability to resolve locally the characteristics of the plasma depletion without relying on assumptions about the mapping of the depletion along magnetic field lines to large latitudinal distances. It presents new information for understanding ESF development and the development of depletions strong enough to produce scintillation.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/51
info:doi/10.1016/j.asr.2010.09.025,
http://www.sciencedirect.com/science/article/pii/S0273117710006423
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Total electron content
Plasma bubbles
Airglow
GPS remote sensing
oai:docs.lib.purdue.edu:easpubs-1049
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Impacts of land-use change and best management practice implementation in a Conservation Effects Assessment Project watershed: Northwest Arkansas
Gitau, Margaret W.
Chaubey, Indrajeet
Gbur, Lichi Chiang
Mohamed, Sayeed
A study was conducted to quantify land use and management changes and their effects on water quality as part of an effort to evaluate the effects of best management practices under the Conservation Effects Assessment Project. This study was focused on the Lincoln Lake watershed, a primarily pastured watershed in northwest Arkansas and one of the watersheds funded under the Conservation Effects Assessment Project competitive grants program. As with a number of other Conservation Effects Assessment Project watersheds, this watershed has undergone substantial land-use change over the past few years. These changes have occurred concurrently with best management practice implementation. Thus, the need has arisen to determine their impacts on watershed water quality. Land-use analyses covering a 12-year period revealed a rapidly changing landscape, with the various land uses experiencing gains and losses at different times. Furthermore, a systematic trend for pastured areas to be replaced by urban land uses was identified, with pastures experiencing a net decline of about 12% during the analyses period. With regard to water quality, downward trends were observed under base and storm flow conditions in the upper reaches (Upper Moores Creek) with significant changes in total phosphorus and total suspended solids (p-values = 0.0153 and 0.0135, respectively). Significant increases in flow and nitrate-nitrogen (p-values = 0.0465 and 0.0927, respectively) were observed in the lower reaches (Lower Moores Creek), while no appreciable changes were observed in one part of the watershed. We conclude that the concurrent implementation of best management practices served to protect water quality from otherwise adverse effects that might have occurred due to a rapid urbanization in the watershed.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/50
info:doi/10.2489/jswc.65.6.353
http://www.jswconline.org/content/65/6/353.full.pdf+html
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1052
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Nitrous Oxide Production in an Eastern Corn Belt Soil: Sources and Redox Range
Hernandez-Ramirez, Guillermo B.
Brouder, Sylvie M.
Smith, Douglas R.
Van Scoyoc, George E.
Michalski, Greg
Nitrous oxide derived from soils is a main contributor to the greenhouse gas effect and a precursor to ozone-depleting substrates; however, the source processes and interacting controls are not well established. This study was conducted to estimate the magnitude and source (nitrification vs. denitrification) of N^sub 2^O production as affected by the form of N fertilizer, soil water content, and redox potential (Eh). Soils from continuous corn (Zea mays L.) experimental plots with a history of eight consecutive years of either side-dressed urea-NH^sub 4^NO^sub 3^ (UAN) or fall liquid swine manure (FM) were collected and N^sub 2^O evolution was traced in both aerobic and anaerobic incubations using ^sup 15^N labeling. Partitioning results were highly variable but suggested that enhanced denitrification occurred after an extreme increase in soil water content (from 45 to 90% water-filled pore space [WFPS]) while a more coupled nitrification-denitrification process drove N^sub 2^O evolution at moderate water content (55% WFPS). Manured soils at high water contents registered shorter duration peaks but with higher overall N^sub 2^O production rates than those observed at moderate water content (7-d weighted average of 0.61 vs. 0.09 μg N^sub 2^O kg^sup -1^ soil h^sup -1^). Under anoxic conditions, manured soils showed higher N^sub 2^O production rates than UAN soils (up to 336 and 145 μg N^sub 2^O kg^sup -1^ soil h^sup -1^, respectively) shortly after flooding, which coincided with a sharp drop in Eh (from 575 to 466 mV). Irrespective of the N source, a narrow, consistent Eh range for N^sub 2^O production occurred under moderate reducing conditions (420-575 mV). These results indicate that soils receiving repeated manure application that are subject to intensive, recurrent soil rewetting events may be prone to higher N^sub 2^O emissions. [PUBLICATION ABSTRACT]
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/53
info:doi/10.2136/sssaj2008.0183
http://search.proquest.com/docview/288485595/1378A1A42A64DD26BAF/2?accountid=13360
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1051
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Interpreting finite strain: Analysis of deformation in analog models
Haq, Saad S. B.
Davis, Dan M.
We investigate the accuracy of strain rates calculated directly from a robust set of velocity measurements that were obtained in controlled experimental settings. We compare the calculated strains and strain rates, and the corresponding deformation style, determined from sets of three vs. four velocity measurements obtained by tracking a dense set of surface markers during experiments. The density of our measurements, in conjunction with a well-understood model deformational setting, allows us to relate the style and magnitude of strains to the underlying structures. We demonstrate that calculating strain values from three measurements can be irrelevant to the geologic structures even if they are mathematically correct, but that one can avoid some of these deceptive results by using quadrangles to calculate strain. We demonstrate the utility of such strain calculations in interpreting strain partitioning in obliquely convergent analog models for continuously and discontinuously deforming materials. In addition, we compare direct calculations with those obtained by determining strains from the derivatives of continuous spline functions that have been fit to the velocity field.
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/52
info:doi/10.1016/j.jsg.2009.03.017
http://www.sciencedirect.com/science/article/pii/S0191814109000443
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Strain
Deformation analysis
Analog model
Strain partitioning
Sandbox experiments
oai:docs.lib.purdue.edu:easpubs-1057
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Old and stable soil organic matter is not necessarily chemically recalcitrant: implications for modeling concepts and temperature sensitivity
Kleber, Markus
Nico, Peter S.
Plante, Alain
Filley, Timothy
Kramer, Marc
Swanston, Christopher
Sollins, Phillip
Soil carbon turnover models generally divide soil carbon into pools with varying intrinsic decomposition rates. Although these decomposition rates are modified by factors such as temperature, texture, and moisture, they are rationalized by assuming chemical structure is a primary controller of decomposition. In the current work, we use near edge X-ray absorption fine structure (NEXAFS) spectroscopy in combination with differential scanning calorimetry (DSC) and alkaline cupric oxide (CuO) oxidation to explore this assumption. Specifically, we examined material from the 2.3-2.6 kg L density fraction of three soils of different type (Oxisol, Alfisol, Inceptisol). The density fraction with the youngest C age (Oxisol, 107 years) showed the highest relative abundance of aromatic groups and the lowest O-alkyl C/aromatic C ratio as determined by NEXAFS. Conversely, the fraction with the oldest C (Inceptisol, 680 years) had the lowest relative abundance of aromatic groups and highest O-alkyl C/aromatic C ratio. This sample also had the highest proportion of thermally labile materials as measured by DSC, and the highest ratio of substituted fatty acids to lignin phenols as indicated by CuO oxidation. Therefore, the organic matter of the Inceptisol sample, with a C age associated with 'passive' pools of carbon (680 years), had the largest proportion of easily metabolizable organic molecules with low thermodynamic stability, whereas the organic matter of the much younger Oxisol sample (107 years) had the highest proportion of supposedly stable organic structures considered more difficult to metabolize. Our results demonstrate that C age is not necessarily related to molecular structure or thermodynamic stability, and we suggest that soil carbon models would benefit from viewing turnover rate as codetermined by the interaction between substrates, microbial actors, and abiotic driving variables. Furthermore, assuming that old carbon is composed of complex or 'recalcitrant' compounds will erroneously attribute a greater temperature sensitivity to those materials than they may actually possess. [ABSTRACT FROM AUTHOR].
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/58
info:doi/10.1111/j.1365-2486.2010.02278.x.
http://web.ebscohost.com/ehost/detail?sid=df2152d8-8614-42a8-8797-2da7313038f9%40sessionmgr10&vid=1&hid=12&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=aph&AN=56943001
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
differential scanning calorimetry (DSC)
near edge X-ray absorption fine structure spectroscopy (NEXAFS)
radiocarbon
recalcitrance
scanning transmission X-ray microscopy (STXM)
soil organic matter
stable isotopes
turnover time.
oai:docs.lib.purdue.edu:easpubs-1056
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Characterizing heart rate variability by scale-dependent Lyapunov exponent
Hu, Jing
Gao, Jianbo
Tung, Wen-wen
Previous studies on heart rate variability (HRV) using chaos theory, fractal scaling analysis, and many other methods, while fruitful in many aspects, have produced much confusion in the literature. Especially the issue of whether normal HRV is chaotic or stochastic remains highly controversial. Here, we employ a new multiscale complexity measure, the scale-dependent Lyapunov exponent (SDLE), to characterize HRV. SDLE has been shown to readily characterize major models of complex time series including deterministic chaos, noisy chaos, stochastic oscillations, random 1/f processes, random Levy processes, and complex time series with multiple scaling behaviors. Here we use SDLE to characterize the relative importance of nonlinear, chaotic, and stochastic dynamics in HRV of healthy, congestive heart failure, and atrial fibrillation subjects. We show that while HRV data of all these three types are mostly stochastic, the stochasticity is different among the three groups.
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/57
info:doi/10.1063/1.3152007
http://chaos.aip.org/resource/1/chaoeh/v19/i2/p028506_s1
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1059
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Global cooling during the Eocene-Oligocene climate transition
Liu, Zhonghui
Pagani, Mark
Zinniker, David
DeConto, Robert
Huber, Matthew
Brinkhuis, Henk
Shah, Sunita R.
Leckie, R. Mark
Pearson, Ann
About 34 million years ago, Earth's climate shifted from a relatively ice-free world to one with glacial conditions on Antarctica characterized by substantial ice sheets. How Earth's temperature changed during this climate transition remains poorly understood, and evidence for Northern Hemisphere polar ice is controversial. Here, we report proxy records of sea surface temperatures from multiple ocean localities and show that the high-latitude temperature decrease was substantial and heterogeneous. High-latitude (45 degrees to 70 degrees in both hemispheres) temperatures before the climate transition were ∼20°C and cooled an average of ∼5°C. Our results, combined with ocean and ice-sheet model simulations and benthic oxygen isotope records, indicate that Northern Hemisphere glaciation was not required to accommodate the magnitude of continental ice growth during this time.
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/60
info:doi/10.1126/science.1166368
http://www.sciencemag.org/content/323/5918/1187
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1061
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
The role of symmetry in the mass independent isotope effect in ozone
Michalski, Greg
Bhattacharya, S. K.
Understanding the internal distribution of “anomalous” isotope enrichments has important implications for validating theoretical postulates on the origin of these enrichments in molecules such as ozone and for understanding the transfer of these enrichments to other compounds in the atmosphere via mass transfer. Here, we present an approach, using the reaction NO2− + O3, for assessing the internal distribution of the Δ17O anomaly and the δ18O enrichment in ozone produced by electric discharge. The Δ17O results strongly support the symmetry mechanism for generating mass independent fractionations, and the δ18O results are consistent with published data. Positional Δ17O and δ18O enrichments in ozone can now be more effectively used in photochemical models that use mass balance oxygen atom transfer mechanisms to infer atmospheric oxidation chemistry.
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/62
info:doi/10.1073/pnas.0812755106
http://www.pnas.org/content/106/14/5493
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oxygen
nitrate
oxidation
oai:docs.lib.purdue.edu:easpubs-1060
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Evaluating evapotranspiration and water-use efficiency of terrestrial ecosystems in the conterminous United States using MODIS and AmeriFlux data
Lu, Xiaoliang
Zhuang, Qianlai
In this study, we used the remotely-sensed data from the Moderate Resolution Imaging Spectrometer (MODIS), meteorological and eddy flux data and an artificial neural networks (ANNs) technique to develop a daily evapotranspiration (ET) product for the period of 2004–2005 for the conterminous U.S. We then estimated and analyzed the regional water-use efficiency (WUE) based on the developed ET and MODIS gross primary production (GPP) for the region. We first trained the ANNs to predict evapotranspiration fraction (EF) based on the data at 28 AmeriFlux sites between 2003 and 2005. Five remotely-sensed variables including land surface temperature (LST), normalized difference vegetation index (NDVI), normalized difference water index (NDWI), leaf area index (LAI) and photosynthetically active radiation (PAR) and ground-measured air temperature and wind velocity were used. The daily ET was calculated by multiplying net radiation flux derived from remote sensing products with EF. We then evaluated the model performance by comparing modeled ET with the data at 24 AmeriFlux sites in 2006. We found that the ANNs predicted daily ET well (R2 = 0.52–0.86). The ANNs were applied to predict the spatial and temporal distributions of daily ET for the conterminous U.S. in 2004 and 2005. The ecosystem WUE for the conterminous U.S. from 2004 to 2005 was calculated using MODIS GPP products (MOD17) and the estimated ET. We found that all ecosystems' WUE-drought relationships showed a two-stage pattern. Specifically, WUE increased when the intensity of drought was moderate; WUE tended to decrease under severe drought. These findings are consistent with the observations that WUE does not monotonously increase in response to water stress. Our study suggests a new water-use efficiency mechanism should be considered in ecosystem modeling. In addition, this study provides a high spatial and temporal resolution ET dataset, an important product for climate change and hydrological cycling studies for the MODIS era.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/61
info:doi/10.1016/j.rse.2010.04.001
http://www.sciencedirect.com/science/article/pii/S0034425710001124
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
MODIS
Evapotranspiration
Artificial neural networks
Water-use efficiency
oai:docs.lib.purdue.edu:easpubs-1062
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Multiple isotope forensics of nitrate in a wild horse poisoning incident
Michalski, Greg
Earman, Sam
Dahman, Christa
Hershey, Rodney L.
Mihevc, Todd
Multiple stable isotope analysis can be a powerful technique in forensic sciences. Oxygen and nitrogen isotopes were used to determine the source of nitrate that was responsible for the poisoning deaths of 71 wild horses in the Nevada desert. The nitrate was present in a water-filled hole known as ‘the Main Lake depression.’ Nitrate from the Main Lake depression had δ18O and δ15N values that were very positive (+32‰, +37‰), and Δ17O values of approximately +2‰. The isotopic data suggested that the most probable source of the nitrate was nitrification of nitrogen from horse manure and urine that had leached into the pond. The δ18O signal suggested that extreme evaporative concentration had occurred, resulting in toxic levels of nitrate accumulating in the Main Lake depression. The study demonstrates the utility of the multiple stable isotope analysis approach for characterizing sources of nitrate.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/63
info:doi/10.1016/j.forsciint.2010.01.012
http://www.sciencedirect.com/science/article/pii/S037907381000037X
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
nitrate
isotopes
nitrogen
horse
oai:docs.lib.purdue.edu:easpubs-1063
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Lake Ice phenology of small lakes: Impacts of climate variability in the Great Lakes region
Mishra, Vimal
Cherkauer, Keith A.
Bowling, Laura C.
Huber, Matthew
Formation of lake ice is common in lakes located in mid and high latitudes. Lake ice plays a vital role in heat storage, controlling lake water temperature, survival of aquatic ecosystems, and maintaining the bio diversity of lakes. Significant warming in air temperature during the cold season (October–May) may lead to reduced ice cover of lakes and eventually disturb the lake's seasonal dynamics. We examined the role of climate variability on lake ice phenology for small inland lakes in the Great Lakes region. The Variable Infiltration Capacity (VIC) model with a physically based lake algorithm was implemented to simulate long term (i.e. 1916–2007) changes in lake ice phenology, as described by the date of ice break-up, date of ice freeze-up, and number of ice-free days. Model performance was evaluated against observed lake ice phenology. A statistically significant increase (0.08–0.21 °C) in air temperature resulted in a significant change (0.2–2.0 days/decade) in lake ice freeze-up and break-up dates. While lake ice freeze-up was strongly associated (correlation > 0.60) with air temperature of the early (October–December) cold season, lake ice break-up was highly associated (correlation = − 0.80) with air temperature during the late (March–May) cold season. The number of ice-free days was affected by the temperature changes during the entire cold season. Lakes located in the southern part of the study domain experienced stronger trends in ice phenology than those located in the northern part. Inter-decadal to decadal scale variability in the number of ice-free days not associated with long-term trends in air temperature were largely driven by the Atlantic Multi-decadal Oscillation (AMO), El-Niño Southern Oscillation (ENSO), and Pacific Decadal Oscillation (PDO).
2011-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/64
info:doi/10.1016/j.gloplacha.2011.01.004
http://www.sciencedirect.com/science/article/pii/S0921818111000130
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
lakes
lake ice
climate variability
climate change
VIC model
oai:docs.lib.purdue.edu:easpubs-1058
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Pacific/North American teleconnection controls on precipitation isotope ratios across the contiguous United States
Liu, Zhongfang
Bowen, Gabriel J.
Kennedy, Casey D.
Large-scale climate teleconnections such as the Pacific/North American (PNA) pattern strongly influence atmospheric processes and continental climate. Here we show that precipitation δ18O values in the contiguous United States are correlated with an index of the PNA pattern. The δ18O/PNA relationship varies across the study region and exhibits two prominent modes, with positive correlation in the western USA and negative correlation in the east. This spatial pattern appears not to reflect variation in local climate variables, but rather primarily reflects differences in atmospheric circulation and moisture sources associated with PNA. Our results suggest that strong antiphase variation in paired paleo-water δ18O proxy records from regions characterized by the two modes of δ18O/PNA correlation, especially in the Midwest and southwestern USA, may provide a robust basis for reconstruction of past variation in the PNA pattern. --------------------------------------------------------------------------------
2011-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/59
info:doi/10.1016/j.epsl.2011.08.037
http://www.sciencedirect.com/science/article/pii/S0012821X11005012
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
precipitation isotope
Pacific/North American
atmospheric circulation
paleoclimate
oai:docs.lib.purdue.edu:easpubs-1065
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Oxfordian magnetostratigraphy of Britain and its correlation to Tethyan regions and Pacific marine magnetic anomalies
Ogg, James G.
Coe, Angela L.
Przybylski, Piotr A.
Wright, John K.
A suite of 11 sections through the Oxfordian (Upper Jurassic) strata in the Dorset and Yorkshire regions of England and the Isle of Skye in Scotland yielded magnetic polarity patterns directly calibrated to the ammonite biostratigraphy of the Boreal and the Subboreal faunal provinces. The sections include the leading candidate for the global stratotype (GSSP) for the Callovian–Oxfordian stage boundary. The mean Oxfordian paleomagnetic pole derived from the Dorset and Yorkshire sections is 71.3°N, 172.6°E (δp = 4.2°, δm = 6.1°). The integrated magneto-biostratigraphic scale is consistent with results from the Sub-Mediterranean faunal province and extends the polarity pattern to the base of the Oxfordian. After adjusting for the estimated durations of ammonite subzones from cycle stratigraphy, the magnetostratigraphy confirms models for marine magnetic anomalies M30 through to M37, including some of the short-duration features recorded by deep-tow magnetic surveys in the western Pacific. The Callovian–Oxfordian boundary (base of Quenstedtoceras mariae Zone) occurs in a normal-polarity zone that is correlated to the youngest part of polarity chron M37n of this extension to the M-sequence.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/66
info:doi/10.1016/j.epsl.2009.11.031
http://www.sciencedirect.com/science/article/pii/S0012821X09006931
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
magnetostratigraphy
oxfordian
ammonite zonation
boreal realm United Kindom
oai:docs.lib.purdue.edu:easpubs-1066
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
The Role of Carbon Dioxide during the Onset of Antarctic Glaciation
Pagani, Markus
Liu, Zhonghiu
Bohaty, Steven
Deconto, Robert
Huber, Matthew
Henderiks, Jorijntje
Earth’s modern climate, characterized by polar ice sheets and large equator-to-pole temperature gradients, is rooted in environmental changes that promoted Antarctic glaciation ~33.7 million years ago. Onset of Antarctic glaciation reflects a critical tipping point for Earth’s climate and provides a framework for investigating the role of atmospheric carbon dioxide (CO2) during major climatic change. Previously published records of alkenone-based CO2 from high- and low-latitude ocean localities suggested that CO2 increased during glaciation, in contradiction to theory. Here, we further investigate alkenone records and demonstrate that Antarctic and subantarctic data overestimate atmospheric CO2 levels, biasing long-term trends. Our results show that CO2 declined before and during Antarctic glaciation and support a substantial CO2 decrease as the primary agent forcing Antarctic glaciation, consistent with model-derived CO2 thresholds.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/67
info:doi/10.1126/science.1203909
http://www.sciencemag.org/content/334/6060/1261
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1068
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Effects of sample size and position from monolith and core methods on the estimation of total root biomass in a temperate grassland ecosystem in Inner Mongolia
Ping, Xiaoyan
Zhou, Guangsheng
Zhuang, Qianlai
Wang, Yanlong
Zuo, Wanqing
Shi, Guangzu
Lin, Xianglei
Wang, Yuhui
Development of an appropriate scheme to accurately sample root biomass is essential for accurate estimation of biomass and carbon budget of grassland. This study evaluated measurement accuracy of the monolith and core methods with different sample sizes and positions in a temperate grassland ecosystem in Inner Mongolia, China. The results indicated that the small core method (3.8-cm-diameter) significantly underestimated total root biomass compared with the large core method (10-cm-diameter), small monolith method (0.25 m2) and large monolith method (1 m2). Total root biomass estimated from the small core method was about 52% less than that from the large monolith method (1 m2). At 95% confidence interval, 10% relative precision could be obtained with five small monoliths, 15 large cores and 65 small cores. The coefficient of variation (CV) for total root biomass decreased logarithmically with increasing sample size for both the monolith and core methods. Compared with the stratified random sampling, core sampling with different fixed positions could not provide reliable estimate of total root biomass. Washing damage and soil lost during extraction might be the major factors controlling the measurement accuracy of total root biomass by core method with small sample size.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/69
info:doi/10.1016/j.geoderma.2009.12.009
http://www.sciencedirect.com/science/article/pii/S001670610900408X
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
grassland
total root biomass
core method
measurement accuracy
sample size
sample position
oai:docs.lib.purdue.edu:easpubs-1067
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
The Complexity of Brownian Processes Run with Nonlinear Clocks
Park, Moongyu
Cushman, John H.
Anomalous diffusion occurs in many branches of physics. Examples include diffusion in confined nanofilms, Richardson turbulence in the atmosphere, near-surface ocean currents, fracture flow in porous formations and vortex arrays in rotating flows. Classically, anomalous diffusion is characterized by a power law exponent related to the mean-square displacement of a particle or squared separation of pairs of particles: 〈|X(t)|2〉 ~tγ. The exponent γ is often thought to relate to the fractal dimension of the underlying process. If γ > 1 the flow is super-diffusive, if it equals 1 it is classical, otherwise it is sub-diffusive. In this work we illustrate how time-changed Brownian position processes can be employed to model sub-, super-, and classical diffusion, while time-changed Brownian velocity processes can be used to model super-diffusion alone. Specific examples presented include transport in turbulent fluids and renormalized transport in porous media. Intuitively, a time-changed Brownian process is a classical Brownian motion running with a nonlinear clock (Bm-nlc). The major difference between classical and Bm-nlc is that the time-changed case has nonstationary increments. An important novelty of this approach is that, unlike fractional Brownian motion, the fractal dimension of the process (space filling character) driving anomalous diffusion as modeled by Bm-nlc positions or velocities does not change with the scaling exponent, γ.
2011-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/68
info:doi/10.1142/S0217984911025481
http://www.worldscientific.com/doi/abs/10.1142/S0217984911025481
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
diffusion
brownian motion
flow in porous media
oai:docs.lib.purdue.edu:easpubs-1069
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Oxfordian magnetostratigraphy of Poland and its correlation to Sub-Mediterranean ammonite zones and marine magnetic anomalies
Przybylski, Piotr A.
Glowniak, E.
Ogg, James G.
Ziólkowski, P.
Sidorczuk, M.
Gutowski, J.
Lewandowski, M.
A nearly continuous magnetostratigraphic polarity pattern was compiled from several ammonite-zoned carbonate successions of southern Poland and from a composite magnetostratigraphy from the Iberian Range of Spain. The array of sections spans the middle two-thirds of the Oxfordian within the Sub-Mediterranean Province (Cordatum through Bifurcatus ammonite zones). The average paleopole calculated from eight of these Polish sections is at 78.5°N, 184.9°E (δp = 2.6°, δm = 3.5°). The Sub-Mediterranean polarity pattern is consistent with an independent polarity pattern derived from the Boreal-realm sections of the British Isles, and improves the inter-correlation between these faunal realms. Cycle stratigraphy published for these ammonite subzones from southern France enabled temporal scaling of the polarity pattern, thereby facilitating correlation to marine magnetic anomalies M28 through M33 as modeled from deep-tow magnetometer surveys in the Western Pacific. The bases of the Middle and Upper Oxfordian substages as defined in the Sub-Mediterranean zonation in Poland correspond approximately to chrons M33 and M29 of that Pacific M-sequence model.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/70
info:doi/10.1016/j.epsl.2009.11.030
http://www.sciencedirect.com/science/article/pii/S0012821X0900692X
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
M-sequence
Oxfordian
timescale
ammonite zones
Tethyan Realm
oai:docs.lib.purdue.edu:easpubs-1070
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Magnetostratigraphic correlation of the Oxfordian-Kimmeridgian boundary
Przybylski, Piotr A.
Ogg, James G.
Wierzbowski, Andrzej
Coe, Angela L.
Hounslow, Mark W.
Wright, John K.
Atrops, Frances
Settles, Erik
A magnetic polarity pattern for Boreal and Sub-Boreal ammonite zones of the Upper Oxfordian to Lower Kimmeridgian was established and confirmed in four British sections, including the proposed Global Boundary Stratotype Section and Point (GSSP) on the Isle of Skye (Scotland) to define the base of the international Kimmeridgian Stage. A coeval pattern for Sub-Mediterranean ammonite zones was compiled from seven sections in Poland, one German section and multi-section composites from France and Spain. The mean paleopole for the European Craton (excluding Spain) at the Oxfordian–Kimmeridgian boundary is 74.2°N, 181.3°E (Α95 = 3.8°). The common magnetic polarity scale enables inter-correlation of ammonite subzones among these three faunal provinces and to the marine magnetic-anomaly M-Sequence. The proposed GSSP at the base of the Pictonia baylei Zone is near the base of an extended interval dominated by reversed polarity, which is interpreted to be Chron M26r. This GSSP level projects to the lower to middle part of the Epipeltoceras bimammatum Subzone, which is the middle subzone of this E. bimammatum Zone in the Sub-Mediterranean standard zonation. In contrast, the traditional placement of the Oxfordian–Kimmeridgian boundary in that Sub-Mediterranean standard zonation (base of Sutneria platynota Zone) is at the base of Chron M25r, or nearly 1 million years younger.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/71
info:doi/10.1016/j.epsl.2009.11.014
http://www.sciencedirect.com/science/article/pii/S0012821X0900661X
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
magnetastratigraphy
Oxfordian-Kimmeridgian boundry
biostratigraphy
marine magnetic
anomaties
oai:docs.lib.purdue.edu:easpubs-1071
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
The Concordiasi Project in Antarctica
Rabier, Florence
Bouchard, Aurelie
Brun, Eric.
Doerenbecher, Alexis.
Guedj, Stephanie
Guidard, Vincent
Karbou, Fatima
Peuch, Vincent-Henri
El Amraoui, Laaziz
Puech, Dominique
Haase, Jennifer S.
The Concordiasi project is making innovative observations of the atmosphere above Antarctica. The most important goals of the Concordiasi are as follows: 1. To enhance the accuracy of weather prediction and climate records in Antarctica through the assimilation of in situ and satellite data, with an emphasis on data provided by hyperspectral infrared sounders. The focus is on clouds, precipitation, and the mass budget of the ice sheets. The improvements in dynamical model analyses and forecasts will be used in chemical-transport models that describe the links between the polar vortex dynamics and ozone depletion, and to advance the understanding of the Earth system by examining the interactions between Antarctica and lower latitudes. 2. To improve our understanding of microphysical and dynamical processes controlling the polar ozone, by providing the first quasi-Lagrangian observations of stratospheric ozone and particles, in addition to an improved characterization of the 3D polar vortex dynamics. Techniques for assimilating these Lagrangian observations are being developed. A major Concordiasi component is a field experiment during the austral springs of 2008–10. The field activities in 2010 are based on a constellation of up to 18 long-duration stratospheric super-pressure balloons (SPBs) deployed from the McMurdo station. Six of these balloons will carry GPS receivers and in situ instruments measuring temperature, pressure, ozone, and particles. Twelve of the balloons will release drop-sondes on demand for measuring atmospheric parameters. Lastly, radiosounding measurements are collected at various sites, including the Concordia station.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/72
info:doi/10.1175/2009BAMS2764.1
http://journals.ametsoc.org/doi/abs/10.1175/2009BAMS2764.1
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1073
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
The minor importance of giant aerosol to precipitation development within small trade wind cumuli observed during RICO
Reiche, C. H.
Lasher-Trapp, Sonia
The present study examines the importance of giant aerosol to precipitation development in marine trade wind cumuli with a new analysis method of a new extensive dataset collected during the Rain in Cumulus over the Ocean (RICO) field campaign. Giant aerosol particles were quantified from clear-air aircraft data, and the precipitation development in the clouds was tracked with dual-polarization radar data. For six different days and multiple clouds on each day, the evolution of the maximum reflectivity, and its associated differential reflectivity, was analyzed. These data were compared with the results of microphysical calculations run within an adiabatic parcel model initialized with the environmental conditions and giant aerosol concentrations on each day of interest. Despite all clouds having formed in a similar maritime environment, this study found substantial variability in the radar echo development both in clouds observed during the same day, and across other days. The maximum reflectivity attained by the clouds appeared to be largely a function of their depth. The radar echo evolution could be represented fairly well by the microphysical parcel model initialized with the observed giant aerosol in some cases but not others. The importance of the giant aerosol to precipitation formation in the small trade wind cumuli appears to be minor: the early radar echoes appear to be more consistent with the development of precipitation by collision and coalescence among droplets formed on the more numerous and smaller cloud condensation nuclei, although the number of giant aerosol appears to have some effect on the actual radar reflectivity values.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/74
info:doi/10.1016/j.atmosres.2009.11.002,
http://www.sciencedirect.com/science/article/pii/S0169809509003226
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
giant aerosol
precipation
trade wind cumulus
RICO
parcel models
oai:docs.lib.purdue.edu:easpubs-1075
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Ambiguous Hydraulic Heads and 14C Activities in Transient Regional Flow
Schwartz, Franklin W.
Sudicky, Edward A.
McLaren, Robert G.
Park, Young-Jin J.
Huber, Matthew
Apted, Mick
A regional flow and transport model is used to explore the implications of significant variability in Pleistocene and Holocene climates on hydraulic heads and 14C activity. Simulations involve a 39 km slice of the Death Valley Flow System through Yucca Mountain toward the Amargosa Desert. The long-time scale over which infiltration has changed (tens-of-thousands of years) is matched by the large physical extent of the flow system (many tens-of-kilometers). Estimated paleo-infiltration rates were estimated using a juniper pollen percentage that extends from the last interglacial (LIG) period (approximately 120 kyrbp) to present. Flow and 14C transport simulations show that groundwater flow changes markedly as a function of paleoclimate. At the last glacial maximum (LGM, 21 kyrbp), the recharge to the flow system was about an order-of-magnitude higher than present, and water table was more than 100 m higher. With large basin time constants, flow is complicated because hydraulic heads at a given location reflect conditions of the past, but at another location the flow may reflect present conditions. This complexity is also manifested by processes that depend on flow, for example 14C transport. Without a model that accounts for the historical transients in recharge for at least the last 20,000 years, there is no simple way to deconvolve the 14C dates to explain patterns of flow.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/76
info:doi/10.1111/j.1745-6584.2009.00655.x
http://onlinelibrary.wiley.com/doi/10.1111/j.1745-6584.2009.00655.x/abstract;jsessionid=80DFEFC40A8052A3F2C280831D1F3DC3.d04t03?systemMessage=Wiley+Online+Library+will+be+disrupted+on+4+August+from+10%3A00-12%3A00+BST+%2805%3A00-07%3A00+EDT%29+for+essential+maintenance
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1078
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
An adaptability limit to climate change due to heat stress
Sherwood, Steven C.
Huber, Matthew
Despite the uncertainty in future climate-change impacts, it is often assumed that humans would be able to adapt to any possible warming. Here we argue that heat stress imposes a robust upper limit to such adaptation. Peak heat stress, quantified by the wet-bulb temperature TW, is surprisingly similar across diverse climates today. TW never exceeds 31 °C. Any exceedence of 35 °C for extended periods should induce hyperthermia in humans and other mammals, as dissipation of metabolic heat becomes impossible. While this never happens now, it would begin to occur with global-mean warming of about 7 °C, calling the habitability of some regions into question. With 11–12 °C warming, such regions would spread to encompass the majority of the human population as currently distributed. Eventual warmings of 12 °C are possible from fossil fuel burning. One implication is that recent estimates of the costs of unmitigated climate change are too low unless the range of possible warming can somehow be narrowed. Heat stress also may help explain trends in the mammalian fossil record.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/79
info:doi/10.1073/pnas.0913352107
http://www.pnas.org/content/107/21/9552
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
climate impacts
global warning
pateclimate
mammalian physiology
oai:docs.lib.purdue.edu:easpubs-1077
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Students’ conceptions about the greenhouse effect, global warming, and climate change
Shepardson, Daniel P.
Niyogi, Dev
Choi, Soyoung
Charusombat, Umarporn
The purpose of this study was to investigate students' conceptions of the greenhouse effect, global warming, and climate change. The study was descriptive in nature and reflected a cross-age design involving the collection of qualitative data from 51 secondary students from three different schools in the Midwest, USA. These data were analyzed for content in an inductive manner to identify student's conceptions. The categories that emerged from the students' responses reflected different degrees of sophistication of students' conceptions about the greenhouse effect, global warming, and climate change. Based on these findings we make curricular recommendations that build on the students' conceptions, the IPCC Findings, the NRC (1996) science education standards, and NOAA's climate literacy framework.
2011-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/78
info:doi/10.1007/s10584-009-9786-9
http://search.proquest.com/docview/852069890?accountid=13360
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1081
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Application of a pseudo simulator to evaluate the sensitivity of parameters in complex watershed models
Sudheer, K. P.
Lakshmi, G.
Chaubey, I.
In this paper, the issue of nonlinear sensitivity analysis for dimensionality reduction in hydrologic model calibration is discussed, and a novel method to quantify the sensitivity of each parameter that considers the nonlinear relationship in the model is presented. The method is based on computing the absolute variation of the nonlinear function represented by the model in its parameter space. The paper discusses the theoretical background of the method and presents the algorithm. The algorithm employs neural network as a pseudo simulator to reduce the computational burden of the analysis. The proposed approach of sensitivity analysis is illustrated through a case study on a physically based distributed hydrologic model. The results indicate that the method is able to rank the parameters effectively, and the ranking can be interpreted in the context of the physical processes being considered by the model.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/82
info:doi/10.1016/j.envsoft.2010.07.007,
http://www.sciencedirect.com/science/article/pii/S1364815210002112
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
psedo simulator
sensitivity analysis
SWAT model
hydrologic modeling
artificial neural network
watershed simulation
oai:docs.lib.purdue.edu:easpubs-1079
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Modeling the influence of a reduced equator-to-pole sea surface temperature gradient on the distribution of water isotopes in the Early/Middle Eocene
Speelman, Eveline N.
Sewall, Jacob O.
Noone, David
Huber, Matthew
der Heydt, Anna
Damsté, Jaap S.
Reichart, Gert Jan
Proxy-based climate reconstructions suggest the existence of a strongly reduced equator-to-pole temperature gradient during the Azolla interval in the Early/Middle Eocene, compared to modern. Changes in the hydrological cycle, as a consequence of a reduced temperature gradient, are expected to be reflected in the isotopic composition of precipitation (δD, δ18O). The interpretation of water isotopic records to quantitatively reconstruct past precipitation patterns is, however, hampered by a lack of detailed information on changes in their spatial and temporal distribution. Using the isotope-enabled version of the National Center for Atmospheric Research (NCAR) atmospheric general circulation model, Community Atmosphere Model v.3 (isoCAM3), relationships between water isotopes and past climates can be simulated. Here we examine the influence of an imposed reduced meridional sea surface temperature gradient on the spatial distribution of precipitation and its isotopic composition in an Early/Middle Eocene setting. As a result of the applied forcings, the Eocene simulation predicts the occurrence of less depleted high latitude precipitation, with δD values ranging only between 0 and −140‰ (compared to Present-day 0 to −300‰). Comparison with Early/Middle Eocene-age isotopic proxy data shows that the simulation accurately captures the main features of the spatial distribution of the isotopic composition of Early/Middle Eocene precipitation over land in conjunction with the aspects of the modeled Early/Middle Eocene climate. Hence, the included stable isotope module quantitatively supports the existence of a reduced meridional temperature gradient during this interval.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/80
info:doi/10.1016/j.epsl.2010.07.026
http://www.sciencedirect.com/science/article/pii/S0012821X10004644
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
hydrogen isotopes
climate modeling
hydrological cycling
paleoclimate
eocene
azolia
oai:docs.lib.purdue.edu:easpubs-1082
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Instability in Leapfrog and Forward-Backward Schemes
Sun, Wen Yih
This paper shows that in the linearized shallow-water equations, the numerical schemes can become weakly unstable for the 2Δx wave in the C grid when the Courant number is 1 in the forward–backward scheme and 0.5 in the leapfrog scheme because of the repeated eigenvalues in the matrices. The instability can be amplified and spread to other waves and smaller Courant number if the diffusion term is included. However, Shuman smoothing can control the instability.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/83
info:doi/10.1175/2009MWR3127.1
http://journals.ametsoc.org/doi/abs/10.1175/2009MWR3127.1
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
data assimilation
shallow-water equations
instability
oai:docs.lib.purdue.edu:easpubs-1083
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Instability in Leapfrog and Forward-Backward Schemes, Part II-Numerical Simulations of Dam Break
Sun, Wen Yih
Following Sun’s approach [17], Shuman smoothing instead of conventional diffusion terms is used in a simple two-time step semi-implicit finite volume scheme to simulate dam break. When the Courant number is less than one, the absolute value of amplification factor of the 1D linearized shallow-water equations is 1 in this new scheme. Compared with the characteristic-based semi-Lagrangian schemes and the Riemann solver, this scheme produces excellent results of free water depth and speed of the shock. Numerical simulations show that the water inside the dam initially moves away radially until water almost depletes near the center; then the water moves back to the center and forms a vertical water column there. This paper proves that Shuman smoothing can be used not only in the linearized shallow-water equations discussed in Sun [17] but also in the nonlinear wave equations to control instability around shocks.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/84
info:doi/10.1016/j.compfluid.2010.11.002,
http://www.sciencedirect.com/science/article/pii/S0045793010003063
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Riemann solver
shallow-water eqyatuibsm senu-implicit scheme
Eigenvalue
characteristic-base
semi-Lagranian
shock
oai:docs.lib.purdue.edu:easpubs-1080
2013-06-26T19:25:31Z
publication:eas
publication:easpubs
publication:sci
Modeled sensitivity of upper thermocline properties to tropical cyclone winds and possible feedbacks on the Hadley circulation
Sriver, Ryan L.
Huber, Matthew
The sensitivity of upper thermocline properties, and global climate, to tropical cyclone (TC) winds is examined using global ocean and atmosphere general circulation models. We combine seven years of global, satellite-based TC wind records with a standard surface wind input data set derived from reanalysis, and we apply idealized factors to TC winds in order to model the ocean's equilibrium response to increases in TC intensities. We find TC-induced vertical ocean mixing impacts upper thermocline properties, such as temperature and mixed layer depth, and the effects are amplified for increasing intensities. The model's ocean heat transport is also affected, but only when TC winds are increased substantially compared to present-day values. Atmospheric model simulations show altered ocean temperature can lead to changes in the mean Hadley circulation. Results suggest increased TC activity may affect global climate by altering the ocean's thermal structure, which could be important for large scale ocean-atmosphere feedbacks.
2010-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/easpubs/81
info:doi/10.1029/2010GL042836
https://docs.lib.purdue.edu/context/easpubs/article/1080/viewcontent/EAS_81_Sriver_Huber.pdf
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
climate dynamics
tropical cyclones
ocean-atmosphere interactions
oai:docs.lib.purdue.edu:easpubs-1084
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Modeling soil thermal and hydrological dynamics and changes of growing season in Alaskan terrestrial ecosystems
Tang, Jinyun
Zhuang, Qianlai
Abundant evidence indicates the growing season has been changed in the Alaskan terrestrial ecosystems in the last century as climate warms. Reasonable simulations of growing season length, onset, and ending are critical to a better understanding of carbon dynamics in these ecosystems. Recent ecosystem modeling studies have been slow to consider the interactive effects of soil thermal and hydrological dynamics on growing season changes in northern high latitudes. Here, we develop a coupled framework to model these dynamics and their effects on plant growing season at a daily time step. In this framework, we (1) incorporate a daily time step snow model into our existing hydrological and soil thermal models and (2) explicitly model the moisture effects on soil thermal conductivity and heat capacity and the effects of active layer depth and soil temperature on hydrological dynamics. The new framework is able to well simulate snow depth and soil temperature profiles for both boreal forest and tundra ecosystems at the site level. The framework is then applied to Alaskan boreal forest and tundra ecosystems for the period 1923-2099. Regional simulations show that (1) for the historical period, the growing season length, onset, and ending, estimated based on the mean soil temperature of the top 20 cm soils, and the annual cycle of snow dynamics, agree well with estimates based on satellite data and other approaches and (2) for the projected period, the plant growing season length shows an increasing trend in both tundra and boreal forest ecosystems. In response to the projected warming, by year 2099, (1) the snow-free days will be increased by 41.0 and 27.5 days, respectively, in boreal forest and tundra ecosystems and (2) the growing season lengths will be more than 28 and 13 days longer in boreal forest and tundra ecosystems, respectively, compared to 2010. Comparing two sets of simulations with and without considering feedbacks between soil thermal and hydrological dynamics, our analyses suggest coupling hydrological and soil thermal dynamics in Alaskan terrestrial ecosystems is important to model ecosystem dynamics, including growing season changes.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/85
info:doi/10.1007/s10584-010-9988-1
http://search.proquest.com/docview/886000803?accountid=13360
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1086
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Regional climate of hazardous convective weather through high-resolution dynamical downscaling
Trapp, Robert J.
Robinson, Eric D.
Baldwin, Michael E.
Diffenbaugh, Noah S.
Schwedler, Benjamin R. J.
We explore the use of high-resolution dynamical downscaling as a means to simulate the regional climatology and variability of hazardous convective-scale weather. Our basic approach differs from a traditional regional climate model application in that it involves a sequence of daily integrations. We use the weather research and forecasting (WRF) model, with global reanalysis data as initial and boundary conditions. Horizontal grid lengths of 4.25 km allow for explicit representation of deep convective storms and hence a compilation of their occurrence statistics over a large portion of the conterminous United States. The resultant 10-year sequence of WRF model integrations yields precipitation that, despite its positive bias, has a diurnal cycle consistent with observations, and otherwise has a realistic geographical distribution. Similarly, the occurrence frequency of short-duration, potentially flooding rainfall compares well to analyses of hourly rain gauge data. Finally, the climatological distribution of hazardous-thunderstorm occurrence is shown to be represented with some degree of skill through a model proxy that relates rotating convective updraft cores to the presence of hail, damaging surface winds, and tornadoes. The results suggest that the proxy occurrences, when coupled with information on the larger-scale atmosphere, could provide guidance on the reliability of trends in the observed occurrences. [ABSTRACT FROM AUTHOR]
2011-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/87
info:doi/10.1007/s00382-010-0826-y
http://web.ebscohost.com/ehost/detail?sid=134e0d84-08ae-4b12-afec-a3e8c05bfef4%40sessionmgr113&vid=1&hid=126&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=aph&AN=63541427
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
heavy rainfall
reanalysis
sever thunderstorms
oai:docs.lib.purdue.edu:easpubs-1088
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Global warming, convective threshold and false thermostats
Williams, Ian N.
Pierrehumbert, Raymond T.
Huber, Matthew
We demonstrate a theoretically expected behavior of the tropical sea surface temperature probability density function (PDF) in future and past (Eocene) greenhouse climate simulations. To first order this consists of a shift to warmer temperatures as climate warms, without change of shape of the PDF. The behavior is tied to a shift of the temperature for deep convection onset. Consequently, the threshold for appearance of high clouds and associated radiative forcing shifts along with temperature. An excess entropy coordinate provides a reference to which the onset of deep convection is invariant, and gives a compact description of SST changes and cloud feedbacks suitable for diagnostics and as a basis for simplified climate models. The results underscore that the typically skewed appearance of tropical SST histograms, with a sharp drop-off above some threshold value, should not be taken as evidence for tropical thermostats.
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/89
info:doi/10.1029/2009GL039849
http://www.agu.org/pubs/crossref/2009/2009GL039849.shtml
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
convection
cloud
feedback
oai:docs.lib.purdue.edu:easpubs-1089
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Twentieth-century droughts and their impacts on terrestrial carbon cycling in China
Xiao, Jingfeng
Zhuang, Qianlai
Liang, Eryuan
Shao, Xuemei
McGuire, A. David
Moody, Aaron
Kicklighter, David W.
Melillo, Jerry M.
Midlatitude regions experienced frequent droughts during the twentieth century, but their impacts on terrestrial carbon balance are unclear. This paper presents a century-scale study of drought effects on the carbon balance of terrestrial ecosystems in China. The authors first characterized the severe extended droughts over the period 1901–2002 using the Palmer drought severity index and then examined how these droughts affected the terrestrial carbon dynamics using tree-ring width chronologies and a process-based biogeochemistry model, the Terrestrial Ecosystem Model (TEM). It is found that China suffered from a series of severe extended droughts during the twentieth century. The major drought periods included 1920–30, 1939–47, 1956–58, 1960–63, 1965–68, 1978–80, and 1999–2002. Most droughts generally reduced net primary productivity (NPP) and net ecosystem productivity (NEP) in large parts of drought-affected areas. Moreover, some of the droughts substantially reduced the countrywide annual NPP and NEP. Out of the seven droughts, three (1920–30, 1965–68, and 1978–80) caused the countrywide terrestrial ecosystems to switch from a carbon sink to a source, and one (1960–63) substantially reduced the magnitude of the countrywide terrestrial carbon sink. Strong decreases in NPP were mainly responsible for the anomalies in annual NEP during these drought periods. Changes in heterotrophic respiration happened in the same direction, but mostly with smaller magnitude. The results show that severe extended droughts had significant effects on terrestrial carbon cycling in China, although future studies should consider other important processes such as drought-induced mortality and regrowth, land-use change, disturbances (e.g., fire), human management (e.g., fertilization and irrigation), and environmental pollution (e.g., ozone pollution, nitrogen deposition). These drought effects are of particular importance in light of projected widespread summer drying in midlatitude regions during the twenty-first century. Future droughts could lead to a reduced terrestrial carbon sink or even a source and exert a positive feedback to the global climate system.
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/90
info:doi/10.1175/2009EI275.1
http://journals.ametsoc.org/doi/abs/10.1175/2009EI275.1
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
drought
carbon cycling
modeling
oai:docs.lib.purdue.edu:easpubs-1090
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Changes of urban wetlands in Wuhan, China, from 1987 to 2005
Xu, Kai
Kong, Chunfang
Liu, Gang
Wu, Chonglong
Deng, Hongbin
Zhang, Yi
Zhuang, Qianlai
Urban wetlands play a significant role in the sustainable development of the urban eco-environment. However, accelerated urbanization has caused rapid changes in urban wetland landscape patterns, which may seriously affect their functions. Based on land-use maps, TM images, and field data from the Wuhan wetlands, the spatiotemporal evolution and wetland landscape pattern were quantitatively analyzed, with reference to landscape ecology indices of diversity, fragmentation, dominance, shape, and dimension. The results showed that: (1) the natural wetland area decreased: lakewetlands andmarshwetlands decreased by 18.71% and 50.3% from1987 to 2005, respectively; (2) artificial wetland area increased by 47.75% in Wuhan over the same period; (3) the lake wetland area ofWuhan declined due to the conversion of large lakes tosmaller ones; (4) the value of the diversity index (H), evenness index (E), and fragmentation index (F) decreased,while the value of the dominance index (D) increased from1987 to 2005; (5) the landscape shape index (LSI) and fractal dimension (FD) of the river wetlands, lake wetlands, bottomland wetlands, and marsh wetlands decreased, while the LSI and FD of the reservoir and pond wetlands increased from1987 to 2005; and (6) natural, societal, and economic, as well as human, activities are major factors for the structural changes in the Wuhan wetland landscape, as revealed by canonical correlation analysis.Results suggest that the ecological environment of urban wetlands should be protected to maximize the services of urban wetland ecosystems in Wuhan, China. [ABSTRACT FROM AUTHOR]
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/91
info:doi/10.1177/0309133309360626
http://web.ebscohost.com/ehost/detail?sid=ae825ac4-f822-444c-9028-713512a0198a%40sessionmgr114&vid=1&hid=123&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=aph&AN=48947346
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
wetlands
landforms
aquatic resources
biotic communities
fragmented landscapes
oai:docs.lib.purdue.edu:easpubs-1092
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Global methane emissions from wetlands, rice paddies, and lakes
Zhuang, Qianlai
Melack, John M.
Zimov, Sergey
Walter, Katey M.
Butenhoff, Christopher L.
Khalil, M. Aslam K.
The current concentration of atmospheric methane is 1774±1.8 parts per billion, and it accounts for 18% of total greenhouse gas radiative forcing [Forster et al., 2007]. Atmospheric methane is 22 times more effective, on a per-unit-mass basis, than carbon dioxide in absorbing long-wave radiation on a 100-year time horizon, and it plays an important role in atmospheric ozone chemistry (e.g., in the presence of nitrous oxides, tropospheric methane oxidation will lead to the formation of ozone). Wetlands are a large source of atmospheric methane, Arctic lakes have recently been recognized as a major source [e.g., Walter et al., 2006], and anthropogenic activities—such as rice agriculture—also make a considerable contribution.
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/93
info:doi/10.1029/2009EO050001
http://onlinelibrary.wiley.com/doi/10.1029/2009EO050001/abstract
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1087
2013-06-12T16:18:31Z
publication:eas
publication:easpubs
publication:sci
Orbitally forced climate changes in the Tasman sector during the Middle Eocene
Warnaar, Jeroen
Bijl, Peter K.
Huber, Matthew
Sloan, Lisa
Brinkhuis, Henk
Röhl, Ursula
Sriver, Ryan
Visscher, Henk
The influence of orbital precession on early Paleogene climate and ocean circulation patterns in the southeast Pacific region is investigated by combining environmental analyses of cyclic Middle Eocene sediments and palynomorph records recovered from ODP Hole 1172A on the East Tasman Plateau with climate model simulations. Integration of results indicates that in the marine realm, direct effects of precessional forcing are not pronounced, although increased precipitation/runoff could have enhanced dinoflagellate cyst production. On the southeast Australian continent, the most pronounced effects of precessional forcing were fluctuations in summer precipitation and temperature on the Antarctic Margin. These fluctuations resulted in vegetational changes, most notably in the distribution of Nothofagus (subgenus Brassospora). The climate model results suggest significant fluctuations in sea ice in the Ross Sea, notably during Austral summers. This is consistent with the influx of Antarctic heterotrophic dinoflagellates in the early part of the studied record. The data demonstrate a strong precessionally driven climate variability and thus support the concept that precessional forcing could have played a role in early Antarctic glaciation via changes in runoff and/or precipitation.
2009-06-21T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/easpubs/88
info:doi/10.1016/j.palaeo.2009.06.023
https://docs.lib.purdue.edu/context/easpubs/article/1087/viewcontent/EAS_88_Sriver_Huber.pdf
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
southern ocean
middle eocene
orbital forcing
model-data comparison
organic-walled dinoflagellate cysts
general circulationmodel
oai:docs.lib.purdue.edu:easpubs-1093
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Spectroscopy of sulfates, clays, and iron oxides in the Jurassic Navajo Sandstone
Bell, Julianne
Bowen, Brenda B.
Martini, Brigette
Analysis of the history of fluid flow and diagenesis in sandstone deposits can potentially furnish insight into how these deposits function as reservoirs. Imaging spectroscopy provides a way to examine surface mineralogy in order to better understand how this mineralogy might have resulted from past fluid flow and diagenesis. Aerially-acquired spectral data, along with spectral data from field samples, are used to help map the mineralogy of a site located within the Jurassic Navajo Sandstone in southern Utah. This site, “Mollies Nipple”, is unusual as it is a butte containing jarosite; an atypical mineral for this area. Mapping the butte's mineralogy in conjunction with its morphology may help provide additional knowledge as to the geologic history of this area. In addition, the presence of hematite concretions as well as the mineral jarosite may potentially make this butte a terrestrial analog for sediments on Mars.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/94
info:doi/10.1109/IGARSS.2010.5650431
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5650431
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1096
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Isoscapes to address large-scale Earth science challenges
Bowen, Gabriel J.
West, Jason B.
Vaughn, Bruce H.
Dawson, Todd E.
Ehleringer, James R.
Fogel, Marilyn L.
Hobson, Keith
Hoogewerff, Jurian
Kendall, Carol
Lai, Chun-Ta
Miller, C. C.
Sugar cane cropping for biofuel production reduces water discharge from a northern Indian basin and threatens downstream communities. Regulators want to partition blame between climate change—induced declines in mountain snowpack and excessive evaporation from poorly managed fields. In the same basin, a tiger is found shot. Is it the nuisance animal that has been tormenting local communities, or is it a different animal poached from the upland forests?
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/97
info:doi/10.1029/2009EO130001
http://onlinelibrary.wiley.com/doi/10.1029/2009EO130001/abstract
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1097
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Refining oxygen isotope analysis in the Nasca region of Peru: An investigation of water sources and archaeological samples
Buzon, M. R.
Conlee, C. A.
Bowen, G. J.
The development of complex societies, irrigation agriculture and sociopolitical transitions are of interest to researchers working in the Nasca region on the south coast of Peru. Occupied for thousands of years, many questions regarding the circumstances of these changes in the area are being investigated. Oxygen isotope analysis provides a method for exploring residential mobility of past peoples during these transitions. This study presents new δ18O data from water sources that would have been used by the ancient inhabitants, providing important information regarding the oxygen isotope variability in the region and the necessary baseline data for migration studies in this region. Our results suggest that the isotopic composition of water sources in the Nasca region is not highly variable. In addition, archaeological human tooth enamel samples from the sites of La Tiza and Pajonal Alto are analysed. The δ18Oc results of the human enamel samples confirm the local nature of the burial population, as suggested by previous strontium isotope analysis (87Sr/86Sr).
2011-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/98
info:doi/10.1002/oa.1151
http://onlinelibrary.wiley.com/doi/10.1002/oa.1151/abstract
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
carbon
La Tiza
mobility
paleodiet
oxygen
oai:docs.lib.purdue.edu:easpubs-1091
2013-06-12T16:13:18Z
publication:eas
publication:easpubs
publication:sci
Simulation of the Middle Miocene climate optimum: implications for future climate
You, Y.
Huber, Matthew
Müller, D. R.
Poulsen, C. J.
Ribbe, J.
Proxy data constraining land and ocean surface paleo-temperatures indicate that the Middle Miocene Climate Optimum (MMCO), a global warming event at ∼15 Ma, had a global annual mean surface temperature of 18.4°C, about 3°C higher than present and equivalent to the warming predicted for the next century. We apply the latest National Center for Atmospheric Research (NCAR) Community Atmosphere Model CAM3.1 and Land Model CLM3.0 coupled to a slab ocean to examine sensitivity of MMCO climate to varying ocean heat fluxes derived from paleo sea surface temperatures (SSTs) and atmospheric carbon dioxide concentrations, using detailed reconstructions of Middle Miocene boundary conditions including paleogeography, elevation, vegetation and surface temperatures. Our model suggests that to maintain MMCO warmth consistent with proxy data, the required atmospheric CO2 concentration is about 460–580 ppmv, narrowed from the most recent estimate of 300–600 ppmv.
2009-02-19T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/easpubs/92
info:doi/10.1029/2008GL036571
https://docs.lib.purdue.edu/context/easpubs/article/1091/viewcontent/EAS_92_Poulsen_Huber.pdf
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Miocene climatic optimum
paleoclimate
paleoclime modeling
oai:docs.lib.purdue.edu:easpubs-1099
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Analysis of the hydrogen and oxygen stable isotope ratios of beverage waters without prior water extraction using isotope ratio infrared spectroscopy
Chesson, Lesley A.
Bowen, G. J.
Ehleringer, James R.
Hydrogen (δ2H) and oxygen (δ18O) stable isotope analysis is useful when tracing the origin of water in beverages, but traditional analytical techniques are limited to pure or extracted waters. We measured the isotopic composition of extracted beverage water using both isotope ratio infrared spectroscopy (IRIS; specifically, wavelength-scanned cavity ring-down spectroscopy) and isotope ratio mass spectrometry (IRMS). We also analyzed beer, sodas, juices, and milk ‘as is’ using IRIS. For IRIS analysis, four sequential injections of each sample were measured and data were corrected for sample-to-sample memory using injections (a) 1-4, (b) 2-4, and (c) 3-4. The variation between δ2H and δ18O values calculated using the three correction methods was larger for unextracted (i.e., complex) beverages than for waters. The memory correction was smallest when using injections 3-4. Beverage water δ2H and δ18O values generally fit the Global Meteoric Water Line, with the exception of water from fruit juices. The beverage water stable isotope ratios measured using IRIS agreed well with the IRMS data and fit 1:1 lines, with the exception of sodas and juices (δ2H values) and beers (δ18O values). The δ2H and δ18O values of waters extracted from beer, soda, juice, and milk were correlated with complex beverage δ2H and δ18O values (r = 0.998 and 0.997, respectively) and generally fit 1:1 lines. We conclude that it is possible to analyze complex beverages, without water extraction, using IRIS although caution is needed when analyzing beverages containing sugars, which can clog the syringe and increase memory, or alcohol, a known spectral interference. Copyright © 2010 John Wiley & Sons, Ltd.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/100
info:doi/10.1002/rcm.4759
http://onlinelibrary.wiley.com/doi/10.1002/rcm.4759/abstract
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1100
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Sensitivity and identifiability of stream flow generation parameters of the SWAT model
Cibin, R.
Sudheer, K. P.
Chaubey, I.
Implementation of sensitivity analysis (SA) procedures is helpful in calibration of models and also for their transposition to different watersheds. The reported studies on SA of Soil and Water Assessment Tool (SWAT) model were mostly focused on identifying parameters for pruning or modifying during the calibration process. This paper presents a sensitivity and identifiability analysis of model parameters that influence stream flow generation in SWAT. The analysis was focused on evaluating the sensitivity of the parameters in different climatic settings, temporal scales and flow regimes. The global sensitivity analysis (GSA) technique based on classical decomposition of variance, Sobol', was employed in this study. The results of the study indicate that modeled stream flow show varying sensitivity to parameters in different climatic settings. The results also suggest that the identifiability of a parameter for a given watershed is a major concern in calibrating the model for the specific watershed, as it might lead to equifinality of parameters. The SWAT model parameters show varying sensitivity in different years of simulation suggesting the requirement for dynamic updation of parameters during the simulation. The sensitivity of parameters during various flow regimes (low, medium and high flow) is also found to be uneven, which suggests the significance of a multi-criteria approach for the calibration of models.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/101
info:doi/10.1002/hyp.7568
http://onlinelibrary.wiley.com/doi/10.1002/hyp.7568/abstract
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
global sensitivity analysis
identifiability analysis
Sobol' method
SWAT
oai:docs.lib.purdue.edu:easpubs-1053
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Early to Middle Miocene monsoon climate in Australia
Herold, Nicholas
Huber, Matthew
Greenwood, D. R.
Muller, R. D.
Seton, M.
The present-day Australian monsoon delivers substantial moisture to the northern regions of a predominantly arid continent. However, the pre-Quaternary history of the Australian monsoon is poorly constrained due to sparse and often poorly dated paleoclimate proxy evidence. Sedimentological and paleontological data suggest that warm, humid, and seasonal environments prevailed in central and north Australia during the Miocene, though it is unclear whether these were products of the Australian monsoon. We perform a series of sensitivity experiments using an atmospheric general circulation model, combined with an offline equilibrium vegetation model, to quantitatively constrain the areal extent of the Miocene monsoon. Our results suggest a weaker than modern monsoon climate during the Miocene. This result is insensitive to atmospheric CO2, although somewhat sensitive to vegetation interactions and the presumed distribution of inland water bodies. None of our Miocene experiments exhibit precipitation rates greater than modern over north Australia, in disagreement with paleoclimate record interpretations. Vegetation modeling indicates that inferred precipitation values from fossil flora and fauna could only support Miocene vegetation patterns if atmospheric CO2 was twice the modern concentration. This suggests that elevated CO2 was critical for sustaining Miocene vegetation.
2011-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/54
info:doi/10.1130/?G31208.1
http://geology.geoscienceworld.org/content/39/1/3.full.pdf+html
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1054
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Characterizing subdiurnal extreme precipitation in the midwestern United States
Hitchens, Nathan M.
Trapp, Robert J.
Baldwin, Michael E.
Gluhovsky, Alexander
This research establishes a methodology to quantify the characteristics of convective cloud systems that produce subdiurnal extreme precipitation. Subdiurnal extreme precipitation events are identified by examining hourly precipitation data from 48 rain gauges in the midwestern United States during the period 1956–2005. Time series of precipitation accumulations for 6-h periods are fitted to the generalized Pareto distribution to determine the 10-yr return levels for the stations. An extreme precipitation event is one in which precipitation exceeds the 10-yr return level over a 6-h period. Return levels in the Midwest vary between 54 and 93 mm for 6-h events. Most of the precipitation contributing to these events falls within 1–2 h. Characteristics of the precipitating systems responsible for the extremes are derived from the National Centers for Environmental Prediction stage II and stage IV multisensor precipitation data. The precipitating systems are treated as objects that are identified using an automated procedure. Characteristics considered include object size and the precipitation mean, variance, and maximum within each object. For example, object sizes vary between 96 and 34 480 km2, suggesting that a wide variety of convective precipitating systems can produce subdiurnal extreme precipitation.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/55
info:doi/10.1175/2009JHM1129.1
http://journals.ametsoc.org/doi/abs/10.1175/2009JHM1129.1
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
Precipitation
Extreme events
Mesoscale systems
North America
Climatology
oai:docs.lib.purdue.edu:easpubs-1055
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Tropical sea temperatures in the high-latitude South Pacific during the Eocene
Hollis, Christopher J.
Handley, Like
Crouch, Erica M.
Morgans, Hugh E. G.
Baker, Joel A.
Creech, John
Collins, Katie S.
Gibbs, Samantha J.
Huber, Matthew
Schouten, Stefan
Zachos, James C
Sea-surface temperature (SST) estimates of ~30 °C from planktic foraminifera and archaeal membrane lipids in bathyal sediments in the Canterbury Basin, New Zealand, support paleontological evidence for a warm subtropical to tropical climate in the early Eocene high-latitude (55°S) southwest Pacific. Such warm SSTs call into question previous estimates based on oxygen isotopes and present a major challenge to climate modelers. Even under hypergreenhouse conditions (2240 ppm CO2), modeled summer SSTs for the New Zealand region do not exceed 20 °C.
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/56
info:doi/10.1130/?G25200A.
http://geology.geoscienceworld.org/content/37/2/99
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1064
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Hydrogen and oxygen in brine shrimp chitin reflect environmental water and dietary isotopic composition
Nielson, Kristine E.
Bowen, Gabriel J.
Hydrogen and oxygen isotope ratios of the common structural biopolymer chitin are a potential recorder of ecological and environmental information, but our understanding of the mechanisms of incorporation of H and O from environmental substrates into chitin is limited. We report the results of a set of experiments in which the isotopic compositions of environmental water and diet were varied independently in order to assess the contribution of these variables to the H and O isotopic composition of Artemia franciscana chitin. Hydrogen isotope ratios of chitin were strongly linearly correlated with both food and water, with approximately 26% of the hydrogen signal reflecting food and approximately 38% reflecting water. Oxygen isotopes were also strongly correlated with the isotopic composition of water and food, but whereas 69% of oxygen in chitin exchanged with environmental water, only 10% was derived from food. We propose that these observations reflect the position-specific, partial exchange of H and O atoms with brine shrimp body water during the processes of digestion and chitin biosynthesis. Comparison of culture experiments with a set of natural samples collected from the Great Salt Lake, UT in 2006 shows that, with some exceptions, oxygen isotope compositions of chitin track those of water, whereas hydrogen isotopes vary inversely with those of lake water. The different behavior of the two isotopic systems can be explained in terms of a dietary shift from allochthonous particulate matter with relatively higher δ2H values in the early spring to autochthonous particulate matter with significantly lower δ2H values in the late summer to autumn. These results suggest oxygen in chitin may be a valuable proxy for the oxygen isotopic composition of environmental water, whereas hydrogen isotope values from the same molecule may reveal ecological and biogeochemical changes within lakes.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/65
info:doi/10.1016/j.gca.2009.12.025
http://www.sciencedirect.com/science/article/pii/S0016703709007765
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1072
2013-06-26T18:56:55Z
publication:eas
publication:easpubs
publication:sci
Roles of atmospheric and land surface data in dynamic regional downscaling
Ray, Deepak K.
Pielke, Roger A., Sr
Nair, Udaysankar S.
Niyogi, Devdutta
In studies dealing with the impact of land use changes on atmospheric processes, a key methodological step is the validation of simulated current conditions. However, regions lacking detailed atmospheric and land use data provide limited information with which to accurately generate control simulations. In this situation, the difference between baseline control simulations and different land use change simulations can be quite different owing to the quality of the atmospheric and land use data sets. Using multiple simulations at the Monteverde cloud forest region of Costa Rica as an example, we show that when a regional climate model is used to study the effect of land use change, it can produce distinctly different results at regional scales, depending on the amount of data available to run the climate simulations. We show that for the specific case of land use change impact studies, the simulation results are very sensitive to the prescribed atmospheric information (e.g., lateral boundary conditions) compared to the land use (surface boundary) information.
2010-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/easpubs/73
info:doi/10.1029/2009JD012218
https://docs.lib.purdue.edu/context/easpubs/article/1072/viewcontent/EAS_73_Ray_Pielke_Nair_Niyogi.pdf
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
atmospheric sciences
earth
climate change
regions
mesoclimatology
oai:docs.lib.purdue.edu:easpubs-1074
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
White-rot basidiomycete-mediated decomposition of C60 fullerol
Schreiner, Kathryn M.
Filley, Timothy R.
Blanchette, Robert A.
Bowen, Brenda B.
Bolskar, Robert D.
Hockaday, William C.
Masiello, Caroline A.
Raebiger, James W.
Industrially produced carbon-based nanomaterials (CNM), including fullerenes and nanotubes, will be introduced into the environment in increasing amounts in the next decades. One likely environmental chemical transformation of C60 is oxidation to C60 fullerol through both abiotic- and biotic-mediated means. Unfortunately, knowledge of the environmental fate of oxidized CNM is lacking. This study used bulk and compound-specific 13C stable isotope ratio mass spectrometry techniques and spectroradiometry analysis to examine the ability of two white rot basidiomycete fungi (Phlebia tremellosa and Trametes versicolor) to metabolize and degrade an oxygenated CNM, C60 fullerol. After 32 weeks of decay, both fungi were able to bleach and oxidize fullerol to CO2. Additionally, the fungi incorporated minor amounts of the fullerol carbon into lipid biomass. These findings are significant in that they represent the first report of direct biodegradation and utilization of any fullerene derivative and provide valuable information about the possible environmental fates of other CNM.
2009-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/75
info:doi/10.1021/es801873q
http://pubs.acs.org/doi/full/10.1021/es801873q
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1076
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Seventh grade students' mental models of the greenhouse effect
Shepardson, Daniel P.
Choi, Soyoung
Niyogi, Dev
Charusombat, Umarporn
This constructivist study investigates 225 student drawings and explanations from three different schools in the midwest in the US, to identify seventh grade students' mental models of the greenhouse effect. Five distinct mental models were derived from an inductive analysis of the content of the students' drawings and explanations: Model 1, a 'greenhouse' for growing plants; Model 2, greenhouse gases cause ozone depletion or formation, causing the Earth to warm; Model 3, greenhouse gases, but no heating mechanism, simply gases in the atmosphere; Model 4, greenhouse gases 'trap' the sun's rays, heating the Earth; and Model 5, the sun's rays are 'bounced' or reflected back and forth between the Earth's surface and greenhouse gases, heating the Earth. Science textbooks are critiqued in light of the students' mental models and curricular and instructional implications are explored. [ABSTRACT FROM AUTHOR]
2011-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/77
info:doi/10.1080/13504620903564549
http://web.ebscohost.com/ehost/detail?sid=93b91c3d-8440-4a8c-b443-2d41d91f1778%40sessionmgr113&vid=1&hid=104&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=tfh&AN=58089785
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
climate change
conceptions
constructivism
oai:docs.lib.purdue.edu:easpubs-1085
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Stable isotope analysis of modern human hair collected from Asia (China, India, Mongolia, and Pakistan)
Thompson, A. H.
Chesson, L. A.
Podlesak, D. W.
Bowen, Gabriel J.
Cerling, T. E.
Ehleringer, J. R.
We report isotopic data (δ2H, δ18O n = 196; δ13C, δ15N n = 142; δ34S n = 85) from human hair and drinking water (δ2H, δ18O n = 67) collected across China, India, Mongolia, and Pakistan. Hair isotope ratios reflected the large environmental isotopic gradients and dietary differences. Geographic information was recorded in H and O and to a lesser extent, S isotopes. H and O data were entered into a recently developed model describing the relationship between the H and O isotope composition of human hair and drinking water in modern USA and pre-globalized populations. This has anthropological and forensic applications including reconstructing environment and diet in modern and ancient human hair. However, it has not been applied to a modern population outside of the USA, where we expect different diet. Relationships between H and O isotope ratios in drinking water and hair of modern human populations in Asia were different to both modern USA and pre-globalized populations. However, the Asian dataset was closer to the modern USA than to pre-globalized populations. Model parameters suggested slightly higher consumption of locally producedfoods in our sampled population than modern USA residents, but lower than pre-globalized populations. The degree of in vivo amino acid synthesis was comparable to both the modern USA and pre-globalized populations. C isotope ratios reflected the predominantly C3-based regional agriculture and C4 consumption in northernChina. C, N, and S isotope ratios supported marine food consumption in some coastal locales. N isotope ratios suggested a relatively low consumption of animal-derived products compared to western populations. Am J Phys Anthropol 2010. © 2009 Wiley-Liss, Inc.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/86
info:doi/10.1002/ajpa.21162
http://onlinelibrary.wiley.com/doi/10.1002/ajpa.21162/abstract;jsessionid=206CA912D7967A4DCCDDF451439B951D.d01t04
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
hair keratin
stable isotope
asia
oai:docs.lib.purdue.edu:easpubs-1094
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Sources of Terrestrial Organic Carbon in the Mississippi Plume Region: Evidence for the Importance of Coastal Marsh Inputs
Bianchi, Thomas S.
Wysocki, Laura A.
Schreiner, Kathryn M.
Filley, Timothy R.
Corbett, D. R.
Kolker, Alexander S.
High sedimentation rates along river-dominated margins make these systems important repositories for organic carbon derived from both allochthonous and autochthonous sources. Using elemental carbon/nitrogen ratios, molecular biomarker (lignin phenol), and stable carbon isotopic (bulk and compound-specific) analyses, this study examined the sources of organic carbon to the Louisiana shelf within one of the primary dispersive pathways of the Mississippi River. Surface sediment samples were collected from stations across the inner, mid, and outer Louisiana shelf, within the Mississippi River plume region, during two cruises in the spring and fall of 2000. Lignin biomarker data showed spatial patterns in terrestrial source plant materials within the river plume, such that sediments near the mouth of the Mississippi River were comparatively less degraded and richer in C 4 plant carbon than those found at mid-depth regions of the shelf. A molecular and stable isotope-based mixing model defining riverine, marsh, and marine organic carbon suggested that the highest organic carbon inputs to the shelf in spring were from marine sources (55–61% marine organic carbon), while riverine organic carbon was the highest (63%) in fall, likely due to lower inputs of marine organic carbon at this time compared with the spring season. This model also indicated that marsh inputs, ranging from 19 to 34% and 3–15% of the organic carbon in spring and fall, respectively, were significantly more important sources of organic carbon on the inner Louisiana shelf than previously suggested. Finally, we propose that the decomposition of terrestrial-derived organic carbon (from the river and local wetlands sources) in mobile muds may serve as a largely unexplored additional source of oxygen-consuming organic carbon in hypoxic bottom waters of the Louisiana shelf.
2011-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/95
info:doi/10.1007/s10498-010-9110-3
http://link.springer.com/article/10.1007/s10498-010-9110-3
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
mobile muds
lignin
chemical biomakers
sediment carbon cycling
Louisiana shelf
compound-specific isotopic analyses
oai:docs.lib.purdue.edu:easpubs-1095
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Statistical and geostatistical mapping of precipitation water isotope ratios
Bowen, Gabriel J.
West, Jason
Dawson, Todd E.
Tung, Kevin P.
More than 5 decades of monitoring has documented wide and systematic variation in the stable isotopic composition of precipitation across the globe. This variation is controlled by climatological processes that govern the source, transport and precipitation of atmospheric moisture. Given the ordered and spatially continuous nature of these processes, variation in precipitation isotopic composition represents a near-ideal system for spatial analysis using geostatistical methods. Spatial analysis of precipitation isotopic composition has a long history, and a wide range of methodologies have been applied to the problem of mapping and predicting isotopic compositions at scales ranging from 102 to 104 km. These range from basic space-only interpolation approaches to more quantitative regression and coupled geostatistical/regression techniques, each with particular benefits and drawbacks. Within the last decade, improved methods for generating quantitative predictions of precipitation isotope ratio distributions and the widespread dissemination of precipitation isoscapes via the world wide web have help spur the development of numerous applications of these data products in climatology, hydrology, ecology, and forensics. Current and future research emphasis on continued improvements in water isotope ratio monitoring and novel isoscapes model parameterizations should help lead to the development of dynamic precipitation isoscapes, incorporating both spatial and temporal variation, and enable new research and applications.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/96
info:doi/10.1007/978-90-481-3354-3_7
http://link.springer.com/chapter/10.1007%2F978-90-481-3354-3_7?LI=true
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1098
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Transpressional rupture of an unmapped fault during the 2010 Haiti earthquake
Calais, Eric
Freed, Andrew
Mattioli, Glen
Amelung, Falk
Jónsson, Sigurjón
Jansma, Pamela
Hong, Sang-Hoon
Dixon, Timothy
Prépetit, Claude
Momplaisir, Roberte
On 12 January 2010, a Mw 7.0 earthquake struck the Port-au-Prince region of Haiti. The disaster killed more than 200,000 people and caused an estimated $8 billion in damages, about 100% of the country’s gross domestic product1. The earthquake was initially thought to have ruptured the Enriquillo–Plantain Garden fault of the southern peninsula of Haiti, which is one of two main strike-slip faults inferred to accommodate the 2 cm yr−1relative motion between the Caribbean and North American plates2, 3. Here we use global positioning system and radar interferometry measurements of ground motion to show that the earthquake involved a combination of horizontal and contractional slip, causing transpressional motion. This result is consistent with the long-term pattern of strain accumulation in Hispaniola. The unexpected contractional deformation caused by the earthquake and by the pattern of strain accumulation indicates present activity on faults other than the Enriquillo–Plantain Garden fault. We show that the earthquake instead ruptured an unmapped north-dipping fault, called the Léogâne fault. The Léogâne fault lies subparallel to—but is different from—the Enriquillo–Plantain Garden fault. We suggest that the 2010 earthquake may have activated the southernmost front of the Haitian fold-and-thrust belt4 as it abuts against the Enriquillo–Plantain Garden fault. As the Enriquillo–Plantain Garden fault did not release any significant accumulated elastic strain, it remains a significant seismic threat for Haiti and for Port-au-Prince in particular.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/99
info:doi/10.1038/ngeo992
http://www.nature.com/ngeo/journal/v3/n11/full/ngeo992.html
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
structural geology
tectonics and geodynamics
seismology
oai:docs.lib.purdue.edu:easpubs-1101
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Quantifying rock uplift rates using channel steepness and cosmogenic nuclide-determined erosion rates: Examples from northern and southern Italy
Cyr, Andrew J.
Granger, Darryl E.
Olivetti, Valerio
Molin, Paola
Rock uplift rates can be difficult to measure over 103–105 yr time scales. If, however, a landscape approaches steady state, where hillslope erosion and rock uplift rates are steady and locally similar, then it should be possible to quantify rock uplift rates from hillslope erosion rates. Here, we test this prediction by comparing channel steepness index values and 10Be catchment-averaged erosion rates to well-constrained rock uplift rates in two landscapes in Italy. The first field area is the Romagna Apennines, northern Italy, where rock uplift rates are relatively uniform, between 0.2 and 0.5 mm/yr (regional mean 0.40 ± 0.15 [SE] mm/yr), and have been steady since 0.9 Ma. The second area is the region around northeastern Sicily and the southernmost Italian peninsula, where rock uplift rates are higher and exhibit a strong spatial gradient, from ∼0.7 to ∼1.6 mm/yr (regional mean 1.09 ± 0.13 [SE] mm/yr). In both regions, channel steepness indices and 10Be erosion rates vary directly with rock uplift rates. Although there is considerable variability in erosion rates, regionally averaged rates in both the northern (0.46 ± 0.04 [SE] mm/yr) and southern (1.21 ± 0.24 [SE] mm/yr) areas accurately measure rock uplift rates. Although channel steepness indices do not quantify rock uplift rates, they are useful for (1) identifying regional patterns of rock uplift, (2) identifying areas where uplift rates might be expected to be uniform, and (3) informing 10Be sampling strategies. This study demonstrates that, together, channel steepness and hillslope erosion rates can provide a powerful tool for determining rock uplift rates.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/102
info:doi/10.1130/L96.1
http://lithosphere.geoscienceworld.org/content/2/3/188
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1103
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
A framework for the incorporation of isotopes and isoscapes in geospatial forensic investigations
Ehleringer, James R.
Thompson, Alexandra H.
Podlesak, David W.
Bowen, Gabriel J.
Chesson, Lesley A.
Cerling, Thure E.
Park, Todd
Dostie, Paul
Schwarcz, Henry
A field that will likely benefit from the developments of isoscapes is forensic sciences, where there is an interest in understanding where evidentiary material might have originated from. This chapter focuses on one small aspect of this large field through exploration of how analyses of hydrogen and oxygen isotopes in water and in human body tissues may be applied to forensic applications where spatially relevant information is required as part of an investigation. The applications of isocapes to forensic sciences are broad, including wildlife, food sourcing, and murder investigations. While the focus of this chapter is on hydrogen and oxygen isotopes, the analyses of heavy elements are an equally important component that can be scaled to include broad geo-spatial patterns.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/104
info:doi/10.1007/978-90-481-3354-3_17
http://link.springer.com/chapter/10.1007/978-90-481-3354-3_17
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
oai:docs.lib.purdue.edu:easpubs-1102
2013-03-14T21:24:03Z
publication:eas
publication:easpubs
publication:sci
Impacts of land use change on climate
Dirmeyer, Paul A.
Niyogi, Dev
de Noblet-Ducoudré, Nathalie
Dickinson, Robert E.
Snyder, P. K.
2010-01-01T08:00:00Z
text
https://docs.lib.purdue.edu/easpubs/103
info:doi/10.1002/joc.2157
http://onlinelibrary.wiley.com/doi/10.1002/joc.2157/abstract
Department of Earth, Atmospheric, and Planetary Sciences Faculty Publications
Purdue University
2058824/oai_dc/100//