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Iowa State University

Geological and Atmospheric Sciences Publications

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Sediment Controls Dynamic Behavior Of A Cordilleran Ice Stream At The Last Glacial Maximum, Ellen A. Cowan, Sarah D. Zellers, Juliane Müller, Maureen H. Walczak, Lindsay L. Worthington, Beth E. Caissie, Wesley A. Clary, John M. Jaeger, Sean P. S. Gulick, Jacob W. Pratt, Alan C. Mix, Stewart J. Fallon Apr 2020

Sediment Controls Dynamic Behavior Of A Cordilleran Ice Stream At The Last Glacial Maximum, Ellen A. Cowan, Sarah D. Zellers, Juliane Müller, Maureen H. Walczak, Lindsay L. Worthington, Beth E. Caissie, Wesley A. Clary, John M. Jaeger, Sean P. S. Gulick, Jacob W. Pratt, Alan C. Mix, Stewart J. Fallon

Geological and Atmospheric Sciences Publications

The uncertain response of marine terminating outlet glaciers to climate change at time scales beyond short-term observation limits models of future sea level rise. At temperate tidewater margins, abundant subglacial meltwater forms morainal banks (marine shoals) or ice-contact deltas that reduce water depth, stabilizing grounding lines and slowing or reversing glacial retreat. Here we present a radiocarbon-dated record from Integrated Ocean Drilling Program (IODP) Site U1421 that tracks the terminus of the largest Alaskan Cordilleran Ice Sheet outlet glacier during Last Glacial Maximum climate transitions. Sedimentation rates, ice-rafted debris, and microfossil and biogeochemical proxies, show repeated abrupt collapses and slow ...


Editorial: Cutting-Edge Analogue Modeling Techniques Applied To Study Earth Systems, Christoph Von Hagke, Jacqueline Reber, Mélody Philippon Oct 2019

Editorial: Cutting-Edge Analogue Modeling Techniques Applied To Study Earth Systems, Christoph Von Hagke, Jacqueline Reber, Mélody Philippon

Geological and Atmospheric Sciences Publications

Our understanding of Earth systems is built on field observations, geological and geophysical investigations and modeling. For over two hundred years, geologists are building analog models to test theories and understand the physics leading to field observations. Analog models do not aim to reproduce nature but rather to simplify the system so that parameters like geometry, kinematics, or dynamics can be isolated and investigated. Analog models allow to investigate complex three-dimensional problems at high-resolution. In addition to deciphering outcrop observations, analog models offer the opportunity to predict structures not accessible for direct observation. Analog models provide a full 4-D view ...


Positive Affective And Behavioral Gains Of First-Year Students In Course-Based Research Across Disciplines, Elizabeth Sandquist, Cinzia Cervato, Craig Ogilvie Jul 2019

Positive Affective And Behavioral Gains Of First-Year Students In Course-Based Research Across Disciplines, Elizabeth Sandquist, Cinzia Cervato, Craig Ogilvie

Geological and Atmospheric Sciences Publications

The Freshmen Research Initiative at Iowa State University promotes student interest and retention in science through introductory course-based undergraduate research experiences (CUREs). Successful strategies for the implementation of CUREs on a large scale in an affordable manner included the use of a postdoctoral coordinator and affiliation with student learning communities. Across multiple disciplines, students in single-semester introductory research courses reported personal gains related to research, to thinking and working like scientists, to attitudes and behaviors of a scientist, and to gains in skills as reported on the Undergraduate Research Student Self-Assessment. Key outcomes related to persistence in STEM, including self-efficacy ...


A Metrics‐Based Analysis Of Seasonal Daily Precipitation And Near‐Surface Temperature Within Seven Coordinated Regional Climate Downscaling Experiment Domains, Justin M. Glisan, Richard Jones, Chris Lennard, Nadia I. Castillo Pérez, Philippe Lucas-Picher, Annette Rinke, Silvina Solman, William J. Gutowski Jr. May 2019

A Metrics‐Based Analysis Of Seasonal Daily Precipitation And Near‐Surface Temperature Within Seven Coordinated Regional Climate Downscaling Experiment Domains, Justin M. Glisan, Richard Jones, Chris Lennard, Nadia I. Castillo Pérez, Philippe Lucas-Picher, Annette Rinke, Silvina Solman, William J. Gutowski Jr.

Geological and Atmospheric Sciences Publications

We compare ensemble mean daily precipitation and near‐surface temperatures from regional climate model simulations over seven Coordinated Regional Climate Downscaling Experiment domains for the winter and summer seasons. We use Taylor diagrams to show the domain‐wide pattern similarity between the model ensemble and the observational data sets. We use the Climatic Research Unit (CRU) and the University of Delaware gridded observations and ERA‐Interim reanalysis data as an additional observationally based estimate of historical climatology. Taylor diagrams determine the relative skill of the seven sets of simulations and quantify these results in terms of center pattern root‐mean ...


Alaska Daily Extreme Precipitation Processes In A Subset Of Cmip5 Global Climate Models, Kevin M. Smalley, Justin M. Glisan, William J. Gutowski Jr. Apr 2019

Alaska Daily Extreme Precipitation Processes In A Subset Of Cmip5 Global Climate Models, Kevin M. Smalley, Justin M. Glisan, William J. Gutowski Jr.

Geological and Atmospheric Sciences Publications

We analyze physical processes leading to daily wintertime (December, January, and February) extreme precipitation events in Alaska between 1986 and 2005. This is done by applying self‐organizing maps to environmental conditions corresponding to National Centers for Environmental Information precipitation, using the European Centre for Medium‐Range Weather Forecasts reanalysis (ERA‐Interim) and Coupled Model Intercomparison Project 5 (CMIP5) global climate selected Global climate model (GCM; selected GCMs). We focus on widespread extreme events, defined as the top 0.1% of daily precipitation occurring on at least six grid boxes on the same day. The self‐organizing maps methodology allows ...


Paired Bulk Organic And Individual Amino Acid Δ15n Analyses Of Bivalve Shell Periostracum: A Paleoceanographic Proxy For Water Source Variability And Nitrogen Cycling Processes, Nina M. Whitney, Beverly J. Johnson, Philip T. Dotsie, Katherine Luzier, Alan D. Wanamaker Jr. Mar 2019

Paired Bulk Organic And Individual Amino Acid Δ15n Analyses Of Bivalve Shell Periostracum: A Paleoceanographic Proxy For Water Source Variability And Nitrogen Cycling Processes, Nina M. Whitney, Beverly J. Johnson, Philip T. Dotsie, Katherine Luzier, Alan D. Wanamaker Jr.

Geological and Atmospheric Sciences Publications

Developing high resolution, well-dated marine proxies of environmental, climatic, and oceanographic conditions is critical in order to advance our understanding of the ocean’s role in the global climate system. While some work has investigated bulk and compound specific stable nitrogen isotopes (δ15N) in bivalve shells as proxies for environmental variability, the small concentrations of nitrogen found in the organic matrix of the shell calcium carbonate (CaCO3) makes developing high resolution records challenging. This study investigates the potential of using the bulk and amino acid δ15N of bivalve periostracum, the protein layer on the outside of the shell, as a ...


Web-Based Student Response Systems And Peer Instruction: A Review And Case Study, Cinzia Cervato Mar 2019

Web-Based Student Response Systems And Peer Instruction: A Review And Case Study, Cinzia Cervato

Geological and Atmospheric Sciences Publications

Cooperative learning and peer instruction are well documented pedagogies that engage students in their learning process. The means to implement cooperative learning in the classroom have evolved from raised hands, colored flashcards, student response systems or “clickers”, to web-based audience response systems that work on any electronic device. This paper briefly reviews available audience response systems and presents a case study on Learning Catalytics, a system designed to enable peer instruction and implement just-in-time teaching pedagogy.


The Impact Of Rheology On The Transition From Stick‐Slip To Creep In A Semi‐Brittle Analog, Thomas Birren, Jacqueline E. Reber Feb 2019

The Impact Of Rheology On The Transition From Stick‐Slip To Creep In A Semi‐Brittle Analog, Thomas Birren, Jacqueline E. Reber

Geological and Atmospheric Sciences Publications

Faults can release energy via a variety of different slip mechanisms ranging from steady creep to fast and destructive earthquakes. Tying the rheology of the crust to various slip dynamics is important for our understanding of plate tectonics and earthquake generation. Here, we propose that the interplay of fractures and viscous flow leads to a spectrum between stick-slip and creep. We use an elasto-visco-plastic rock analog (Carbopol U-21) where we vary the yield stress to investigate its impact on slip dynamics in shear experiments. The experiments are performed using a simple shear apparatus, which provides distributed shear across the entire ...


Pervasively Anoxic Surface Conditions At The Onset Of The Great Oxidation Event: New Multi-Proxy Constraints From The Cooper Lake Paleosol, Michael G. Babechuk, Nadine Weimar, Ilka C. Kleinhanns, Suemeyya Eroglu, Elizabeth D. Swanner, Gavin G. Kenny, Balz S. Kamber, Ronny Schoenberg Jan 2019

Pervasively Anoxic Surface Conditions At The Onset Of The Great Oxidation Event: New Multi-Proxy Constraints From The Cooper Lake Paleosol, Michael G. Babechuk, Nadine Weimar, Ilka C. Kleinhanns, Suemeyya Eroglu, Elizabeth D. Swanner, Gavin G. Kenny, Balz S. Kamber, Ronny Schoenberg

Geological and Atmospheric Sciences Publications

Oceanic element inventories derived from marine sedimentary rocks place important constraints on oxidative continental weathering in deep time, but there remains a scarcity in complementary observations directly from continental sedimentary reservoirs. This study focuses on better defining continental weathering conditions near the Archean-Proterozoic boundary through the multi-proxy (major and ultra-trace element, Fe and Cr stable isotopes, μ-XRF elemental mapping, and detrital zircon U-Pb geochronology) investigation of the ca. 2.45 billion year old (giga annum, Ga) Cooper Lake paleosol (saprolith), developed on a sediment-hosted mafic dike within the Huronian Supergroup (Ontario, Canada).

Throughout the variably altered Cooper Lake saprolith, ratios ...


North American Extreme Precipitation Events And Related Large-Scale Meteorological Patterns: A Review Of Statistical Methods, Dynamics, Modeling, And Trends, Mathew Barlow, William J. Gutowski Jr., John R. Gyakum, Richard W. Katz, Young‑Kwon Lim, Russ S. Schumacher, Michael F. Wehner, Laurie Agel, Michael Bosilovich, Allison Collow, Alexander Gershunov, Richard Grotjahn, Ruby Leung, Shawn Milrad, Seung‑Ki Min Jan 2019

North American Extreme Precipitation Events And Related Large-Scale Meteorological Patterns: A Review Of Statistical Methods, Dynamics, Modeling, And Trends, Mathew Barlow, William J. Gutowski Jr., John R. Gyakum, Richard W. Katz, Young‑Kwon Lim, Russ S. Schumacher, Michael F. Wehner, Laurie Agel, Michael Bosilovich, Allison Collow, Alexander Gershunov, Richard Grotjahn, Ruby Leung, Shawn Milrad, Seung‑Ki Min

Geological and Atmospheric Sciences Publications

This paper surveys the current state of knowledge regarding large-scale meteorological patterns (LSMPs) associated with short-duration (less than 1 week) extreme precipitation events over North America. In contrast to teleconnections, which are typically defined based on the characteristic spatial variations of a meteorological field or on the remote circulation response to a known forcing, LSMPs are defined relative to the occurrence of a specific phenomenon—here, extreme precipitation—and with an emphasis on the synoptic scales that have a primary influence in individual events, have medium-range weather predictability, and are well-resolved in both weather and climate models. For the LSMP ...


Hot Days And Tropical Nights In Nigeria: Trends And Associated Large-Scale Features, Abayomi A. Abatan, Babatunde J. Abiodun, Elijah J. Adefisan, William J. Gutowski Jr. Dec 2018

Hot Days And Tropical Nights In Nigeria: Trends And Associated Large-Scale Features, Abayomi A. Abatan, Babatunde J. Abiodun, Elijah J. Adefisan, William J. Gutowski Jr.

Geological and Atmospheric Sciences Publications

The impact on society of extreme temperature events is enormous. This study examines the temporal evolution and trends in mean temperatures (minimum temperature, TN and maximum temperature, TX) and warm extremes in Nigeria as well as in three regions in Nigeria (Guinea, Savanna, and Sahel) using homogenized daily TN and TX for the period 1971–2012. Warm extremes are defined as days with TX > 35 °C (HotD) and nights with TN > 20°C (TropN). The modified Mann-Kendall test is used to calculate and assess the statistical significance of trends in the indices. The results at annual and seasonal (JFM, AMJ ...


Glacial Erosion Driven By Variations In Meltwater Drainage, S. V. Ugelvig, D. L. Egholm, R. S. Anderson, Neal R. Iverson Nov 2018

Glacial Erosion Driven By Variations In Meltwater Drainage, S. V. Ugelvig, D. L. Egholm, R. S. Anderson, Neal R. Iverson

Geological and Atmospheric Sciences Publications

The subglacial processes of abrasion and quarrying are thought to be primarily responsible for bedrock erosion by glaciers. While theory points to sliding speed as the dominant control on abrasion, rates of quarrying are likely scaled by a more complex combination of sliding speed, effective pressure, bed roughness, and short‐term water‐pressure fluctuations. Here we pair a model for quarrying based on statistical characterization of bedrock strength with a model for subglacial hydrology that describes the temporal evolution of cavities under the influence of variations in sliding speed and effective pressure. Using a finite element model, we simulate the ...


Frackfinder: A Matlab Toolbox For Computing 3‐D Hydraulic Conductivity Tensors For Fractured Porous Media, Nathan L. Young, Jacqueline E. Reber, William W. Simpkins Oct 2018

Frackfinder: A Matlab Toolbox For Computing 3‐D Hydraulic Conductivity Tensors For Fractured Porous Media, Nathan L. Young, Jacqueline E. Reber, William W. Simpkins

Geological and Atmospheric Sciences Publications

Fractures in porous media have been documented extensively. However, they are often omitted from groundwater flow and mass transport models due to a lack of data on fracture hydraulic properties and the computational burden of simulating fractures explicitly in large model domains. We present a MATLAB toolbox, FracKfinder, that automates HydroGeoSphere (HGS), a variably-saturated, control volume finite-element model, to simulate an ensemble of discrete fracture network (DFN) flow experiments on a single cubic model mesh containing a stochastically-generated fracture network. Because DFN simulations in HGS can simulate flow in both a porous media and a fracture domain, this toolbox computes ...


Geochemical Characterization Of Two Ferruginous Meromictic Lakes In The Upper Midwest, Usa, Nicholas Lambrecht, Chad Wittkop, Sergei Katsev, Mojtaba Fakhraee, Elizabeth D. Swanner Oct 2018

Geochemical Characterization Of Two Ferruginous Meromictic Lakes In The Upper Midwest, Usa, Nicholas Lambrecht, Chad Wittkop, Sergei Katsev, Mojtaba Fakhraee, Elizabeth D. Swanner

Geological and Atmospheric Sciences Publications

To elucidate the role of (bio)geochemical processes that fueled iron and carbon cycling in early Earth oceans, modern environments with similar geochemical conditions are needed. As the range of chemical, physical, and biological attributes of the Precambrian oceans must have varied in time and space, lakes of different compositions are useful to ask and answer different questions. Tropical Lake Matano (Indonesia), the largest known ferruginous lake, and Lake Pavin (France), a meromictic crater lake, are the two best studied Precambrian ocean analogs. Here we present seasonal geochemical data from two glacially formed temperate ferruginous lakes: Brownie Lake (MN) and ...


Comparison Of Flow And Transport Experiments On 3d Printed Micromodels With Direct Numerical Simulations, Francesca Watson, Julien Maes, Sebastian Geiger, Eric Mackay, Mike Singleton, Thomas Mcgravie, Terry Anouilh, T. Dawn Jobe, Shuo Zhang, Susan Agar, Sergey Ishutov, Franciszek Hasiuk Aug 2018

Comparison Of Flow And Transport Experiments On 3d Printed Micromodels With Direct Numerical Simulations, Francesca Watson, Julien Maes, Sebastian Geiger, Eric Mackay, Mike Singleton, Thomas Mcgravie, Terry Anouilh, T. Dawn Jobe, Shuo Zhang, Susan Agar, Sergey Ishutov, Franciszek Hasiuk

Geological and Atmospheric Sciences Publications

Understanding pore-scale flow and transport processes is important for understanding flow and transport within rocks on a larger scale. Flow experiments on small-scale micromodels can be used to experimentally investigate pore-scale flow. Current manufacturing methods of micromodels are costly and time consuming. 3D printing is an alternative method for the production of micromodels. We have been able to visualise small-scale, single-phase flow and transport processes within a 3D printed micromodel using a custom-built visualisation cell. Results have been compared with the same experiments run on a micromodel with the same geometry made from polymethyl methacrylate (PMMA, also known as Perspex ...


Statistics Of Multi‐Year Droughts From The Method For Object‐Based Diagnostic Evaluation, Abayomi A. Abatan, William J. Gutowski Jr., Caspar M. Ammann, Laurna Kaatz, Barbara B. Brown, Lawrence Buja, Randy Bullock, Tressa Fowler, Eric Gilleland, John Halley Gotway Jun 2018

Statistics Of Multi‐Year Droughts From The Method For Object‐Based Diagnostic Evaluation, Abayomi A. Abatan, William J. Gutowski Jr., Caspar M. Ammann, Laurna Kaatz, Barbara B. Brown, Lawrence Buja, Randy Bullock, Tressa Fowler, Eric Gilleland, John Halley Gotway

Geological and Atmospheric Sciences Publications

This study uses the Method for Object-based Diagnostic Evaluation (MODE) technique to examine and compare the statistics of drought attributes over the upper Colorado River basin (UCRB). The drought objects are based on the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI) on a 36-month timescale (SPI36 and SPEI36, respectively). The drought indicators are calculated using monthly precipitation as well as minimum and maximum temperatures from the Precipitation- Elevation Regression on Independent Slopes Model datasets from 1948 to 2012. MODE uses paired object attributes such as centroid distance, orientation angle, area ratio, and intersection area and a ...


Combining Academics And Social Engagement: A Major-Specific Early Alert Method To Counter Student Attrition In Science, Technology, Engineering, And Mathematics, Andrew J. Sage, Cinzia Cervato, Ulrike Genschel, Craig Ogilvie Jun 2018

Combining Academics And Social Engagement: A Major-Specific Early Alert Method To Counter Student Attrition In Science, Technology, Engineering, And Mathematics, Andrew J. Sage, Cinzia Cervato, Ulrike Genschel, Craig Ogilvie

Geological and Atmospheric Sciences Publications

Students are most likely to leave science, technology, engineering, and mathematics (STEM) majors during their first year of college. We developed an analytic approach using random forests to identify at-risk students. This method is deployable midway through the first semester and accounts for academic preparation, early engagement in university life, and performance on midterm exams. By accounting for cognitive and noncognitive factors, our method achieves stronger predictive performance than would be possible using cognitive or noncognitive factors alone. We show that it is more difficult to predict whether students will leave STEM than whether they will leave the institution. More ...


A Preliminary Examination Of Wrf Ensemble Prediction Of Convective Mode Evolution, Bradley R. Carlberg, William A. Gallus Jr., Kristie J. Franz Jun 2018

A Preliminary Examination Of Wrf Ensemble Prediction Of Convective Mode Evolution, Bradley R. Carlberg, William A. Gallus Jr., Kristie J. Franz

Geological and Atmospheric Sciences Publications

Accurately simulating convective mode evolution can assist forecasters in the severe weather warning process. A few prior studies have examined the skill of simulating convective modes using single, deterministic forecasts. The present study extends the earlier evaluations to a small, four-member ensemble, with each member incorporating varying initial and lateral boundary conditions, microphysics schemes, and planetary boundary layer schemes. Simulated convective modes from thirty-two 12-h simulations were categorized into nine classifications using a classification scheme developed from previous studies. Multiple methods were used to derive forecasts of these convective classifications, creating an hourly deterministic ensemble mode forecast and probabilistic forecasts ...


Evaluation Of Regional Very Heavy Precipitation Events During The Summer Season Using Narccap Contemporary Simulations, Sho Kawazoe, William J. Gutowski Jr. Apr 2018

Evaluation Of Regional Very Heavy Precipitation Events During The Summer Season Using Narccap Contemporary Simulations, Sho Kawazoe, William J. Gutowski Jr.

Geological and Atmospheric Sciences Publications

Regional climate models (RCMs) from the North American Regional Climate Change Assessment Program (NARCCAP) are compared with the two gridded precipitation datasets (Climate Prediction Center (CPC) and the University of Washington (UW)) and the North American Regional Reanalysis (NARR) to examine if RCMs are able to reproduce very heavy precipitation under similar physical conditions seen in observations. The analysis focuses on contemporary climate (1982-1999) in an upper Mississippi region during the summer (June-July-August) months and utilizes output from NARCCAP RCMs forced with a reanalysis and atmosphere-ocean global climate models (AOGCMs).

The NARCCAP models generally reproduce the precipitation frequency vs. intensity ...


Open Ocean Vs. Continentally-Derived Iron Cycles Along The Neoarchean Campbellrand-Malmani Carbonate Platform, South Africa, Suemeyya Eroglu, Ronny Schoenberg, Sakura Pascarelli, Nicolas J. Beukes, Ilka C. Kleinhanns, Elizabeth D. Swanner Apr 2018

Open Ocean Vs. Continentally-Derived Iron Cycles Along The Neoarchean Campbellrand-Malmani Carbonate Platform, South Africa, Suemeyya Eroglu, Ronny Schoenberg, Sakura Pascarelli, Nicolas J. Beukes, Ilka C. Kleinhanns, Elizabeth D. Swanner

Geological and Atmospheric Sciences Publications

The deposition of large amounts of mixed-valence Fe minerals in iron formations during the Archean and Paleoproterozoic indicates that the Fe(II)aq (aqueous) content of coeval anoxic seawater was likely several hundred μM, compared to ca. 1 to 20 nM of the modern oxygenated ocean. It has been suggested that oxygen production along shallow marine continental shelves, which probably started several hundred million years before the rise of atmospheric oxygen, effectively oxidized Fe(II)aq from deeper seawater and removed it as Fe(III)ppt(poorly soluble precipitates). However, the reconstruction of the marine Fe cycle during the Archean ...


Oxic Fe(Iii) Reduction Could Have Generated Fe(Ii) In The Photic Zone Of Precambrian Seawater, Elizabeth D. Swanner, Markus Maisch, Wenfang Wu, Andreas Kappler Mar 2018

Oxic Fe(Iii) Reduction Could Have Generated Fe(Ii) In The Photic Zone Of Precambrian Seawater, Elizabeth D. Swanner, Markus Maisch, Wenfang Wu, Andreas Kappler

Geological and Atmospheric Sciences Publications

Many marine Precambrian iron formations (IF) record deep anoxic seawater enriched in Fe(II) (i.e. ferruginous) overlain by mildly oxygenated surface water. This is reflected by iron-rich sediments forming in deep basins, and relatively iron-poor sediments forming in shallow, sunlit waters. Such an iron gradient is often interpreted as a redox interface where dissolved Fe(II) was oxidized and precipitated as Fe(III)-bearing minerals. As such, sedimentary iron enrichments are proxy to the progressive oxidation of the oceans through geological time. However, this interpretation is founded on the assumption that Fe(II) could not persist within an oxygenated ...


Authentic Research In An Introductory Geology Laboratory And Student Reflections: Impact On Nature Of Science Understanding And Science Self-Efficacy, Elizabeth Moss, Cinzia Cervato, Ulrike Genschel, Lori Ihrig, Craig A. Ogilvie Feb 2018

Authentic Research In An Introductory Geology Laboratory And Student Reflections: Impact On Nature Of Science Understanding And Science Self-Efficacy, Elizabeth Moss, Cinzia Cervato, Ulrike Genschel, Lori Ihrig, Craig A. Ogilvie

Geological and Atmospheric Sciences Publications

This study examines the effects of an extended authentic research experience on students’ understanding of the nature of science (NOS) and self-efficacy toward science. The curriculum of an introductory physical geology lab was transformed to include a six-week, student-driven research project focused on local groundwater and surface water issues. Students’ NOS understanding was measured by using a modified version of the Student Understanding of Science and Scientific Inquiry questionnaire (n = 181) and their science self-efficacy using a modified vocational self-efficacy survey (n = 179). Data were collected on students during four semesters. We found that the combination of having students explicitly ...


Validating 3d-Printed Porous Proxies By Tomography And Porosimetry, Franciszek J, Hasiuk, Sergey Ishutov, Artur Pacyga Jan 2018

Validating 3d-Printed Porous Proxies By Tomography And Porosimetry, Franciszek J, Hasiuk, Sergey Ishutov, Artur Pacyga

Geological and Atmospheric Sciences Publications

Purpose. The objective of this study was to evaluate how accurately a 3D printer could manufacture basic porous models. Geoscience research is evolving toward numerical prediction of porous rock properties, but laboratory tests are still considered standard practice. 3D printing digital designs of porous models (proxies) is a way to bridge the gap between these two realms of inquiry.

Design/methodology/approach. Digital designs of simple porous models were 3D-printed on an inkjet-style (polyjet) 3D printer. Porosity and pore-throat size distribution of proxies were measured with helium porosimetry, mercury porosimetry, and computed tomography image analysis. Laboratory results on proxies were ...


Comparison Of Brittle- And Viscous Creep In Quartzites: Implications For Semi-Brittle Flow Of Rocks, Jacqueline E. Reber, Matej Pec Jan 2018

Comparison Of Brittle- And Viscous Creep In Quartzites: Implications For Semi-Brittle Flow Of Rocks, Jacqueline E. Reber, Matej Pec

Geological and Atmospheric Sciences Publications

The co-existence and interaction between brittle and viscous deformation processes contributes to the integrated strength of the crust and results in a wide range of energy-release mechanisms ranging from earthquakes to creep. Here, we compare flow laws derived for quartz-rich rocks deforming by brittle creep, wet dislocation power-law creep and dissolution-precipitation creep. We investigate theoretically the conditions when both brittle and viscous processes contribute significantly to deformation provided that all processes act independently and in parallel. Utilizing a comprehensive data set for deformation experiments in quartz-rich rocks, we find that the transition between deformation mechanisms is strongly dependent on input ...


Oceanographic And Climatic Change In The Bering Sea, Last Glacial Maximum To Holocene, Ben M. Pelto, Beth E. Caissie, Steven T. Petsch, Julie Brigham-Grette Jan 2018

Oceanographic And Climatic Change In The Bering Sea, Last Glacial Maximum To Holocene, Ben M. Pelto, Beth E. Caissie, Steven T. Petsch, Julie Brigham-Grette

Geological and Atmospheric Sciences Publications

Post‐glacial sea level rise led to a direct connection between the Arctic and Pacific Oceans via the Bering Strait. Consequently, the Bering Sea experienced changes in connectivity, size, and sediment sources that were among the most drastic of any ocean basin in the past 30,000 years. However, the sedimentary response to the interplay between climate change and sea level rise in high‐latitude settings such as Beringia remains poorly resolved. To ascertain changes in sediment delivery, productivity, and regional oceanography from the Last Glacial Maximum (LGM) to the Holocene, we analyzed sedimentological, geochemical, and isotopic characteristics of three ...


A Stalagmite Test Of North Atlantic Sst And Iberian Hydroclimate Linkages Over The Last Two Glacial Cycles, Rhawn F. Denniston, Amanda N. Houts, Yemane Asmerom, Alan D. Wanamaker Jr., Jonathan A. Haws, Victor J. Polyak, Diana L. Thatcher, Setsen Altan-Ochir, Alyssa C. Borowske, Sebastian F. M. Breitenbach, Caroline C. Ummenhofer, Frederico T. Regala, Michael M. Benedetti, Nuno F. Bicho Jan 2018

A Stalagmite Test Of North Atlantic Sst And Iberian Hydroclimate Linkages Over The Last Two Glacial Cycles, Rhawn F. Denniston, Amanda N. Houts, Yemane Asmerom, Alan D. Wanamaker Jr., Jonathan A. Haws, Victor J. Polyak, Diana L. Thatcher, Setsen Altan-Ochir, Alyssa C. Borowske, Sebastian F. M. Breitenbach, Caroline C. Ummenhofer, Frederico T. Regala, Michael M. Benedetti, Nuno F. Bicho

Geological and Atmospheric Sciences Publications

Close coupling of Iberian hydroclimate and North Atlantic sea surface temperature (SST) during recent glacial periods has been identified through the analysis of marine sediment and pollen grains co-deposited on the Portuguese continental margin. While offering precisely correlatable records, these time series have lacked a directly dated, site-specific record of continental Iberian climate spanning multiple glacial cycles as a point of comparison. Here we present a high-resolution, multi-proxy (growth dynamics and δ13C, δ18O, and δ234U values) composite stalagmite record of hydroclimate from two caves in western Portugal across the majority of the last two glacial cycles (∼220 ...


Evaluation Of The Atmosphere–Land–Ocean–Sea Ice Interface Processes In The Regional Arctic System Model Version 1 (Rasm1) Using Local And Globally Gridded Observations, Michael A. Brunke, John J. Cassano, Nicholas Dawson, Alice K. Duvivier, William J. Gutowski Jr., Joseph Hamman, Wieslaw Maslowski, Bart Nijssen, J. E. Jack Reeves Eyre, José C. Renteria, Andrew Roberts, Xubin Zeng Jan 2018

Evaluation Of The Atmosphere–Land–Ocean–Sea Ice Interface Processes In The Regional Arctic System Model Version 1 (Rasm1) Using Local And Globally Gridded Observations, Michael A. Brunke, John J. Cassano, Nicholas Dawson, Alice K. Duvivier, William J. Gutowski Jr., Joseph Hamman, Wieslaw Maslowski, Bart Nijssen, J. E. Jack Reeves Eyre, José C. Renteria, Andrew Roberts, Xubin Zeng

Geological and Atmospheric Sciences Publications

The Regional Arctic System Model version 1 (RASM1) has been developed to provide high-resolution simulations of the Arctic atmosphere–ocean–sea ice–land system. Here, we provide a baseline for the capability of RASM to simulate interface processes by comparing retrospective simulations from RASM1 for 1990–2014 with the Community Earth System Model version 1 (CESM1) and the spread across three recent reanalyses. Evaluations of surface and 2 m air temperature, surface radiative and turbulent fluxes, precipitation, and snow depth in the various models and reanalyses are performed using global and regional datasets and a variety of in situ datasets ...


A Theoretical Model Of Drumlin Formation Based On Observations At Múlajökull, Iceland, Neal R. Iverson, R. G. Mccracken, L. K. Zoet, Í. Ö. Benediktsson, A. Schomacker, M. D. Johnson, J. Woodard Dec 2017

A Theoretical Model Of Drumlin Formation Based On Observations At Múlajökull, Iceland, Neal R. Iverson, R. G. Mccracken, L. K. Zoet, Í. Ö. Benediktsson, A. Schomacker, M. D. Johnson, J. Woodard

Geological and Atmospheric Sciences Publications

The drumlin field at the surge‐type glacier, Múlajökull, provides an unusual opportunity to build a model of drumlin formation based on field observations in a modern drumlin‐forming environment. These observations indicate that surges deposit till layers that drape the glacier forefield, conform to drumlin surfaces, and are deposited in shear. Observations also indicate that erosion helps create drumlin relief, effective stresses in subglacial till are highest between drumlins, and during quiescent flow, crevasses on the glacier surface overlie drumlins while subglacial channels occupy intervening swales. In the model, we consider gentle undulations on the bed bounded by subglacial ...


Further Evaluation Of Probabilistic Convective Precipitation Forecasts Using The Qpf–Pop Neighborhood Relationship, Michael C. Kochasic, William A. Gallus Jr., Christopher J. Schaffer Aug 2017

Further Evaluation Of Probabilistic Convective Precipitation Forecasts Using The Qpf–Pop Neighborhood Relationship, Michael C. Kochasic, William A. Gallus Jr., Christopher J. Schaffer

Geological and Atmospheric Sciences Publications

A neighborhood postprocessing approach that relates quantitative precipitation forecasts (QPF) to probability of precipitation (PoP) forecasts applied to a single model run was found by Schaffer et al. to be as good as traditional ensemble-based approaches using 10 members in 30-h forecasts of convective precipitation. The present study evaluates if PoP forecasts derived from additional variations of the approach can improve PoP forecasts further compared with previous methods. Ensemble forecasts from the Center for Analysis and Prediction of Storms (CAPS) are used for neighborhood tests comparing a single model run and a traditional ensemble. In the first test, PoP forecasts ...


Pristine Nocturnal Convective Initiation: A Climatology And Preliminary Examination Of Predictability, Sean Stelten, William A. Gallus Jr. Aug 2017

Pristine Nocturnal Convective Initiation: A Climatology And Preliminary Examination Of Predictability, Sean Stelten, William A. Gallus Jr.

Geological and Atmospheric Sciences Publications

The prediction of convective initiation remains a challenge to forecasters in the Great Plains, especially for elevated events at night. This study examines a subset of 287 likely elevated nocturnal convective initiation events that occurred with little or no direct influence from surface boundaries or preexisting convection over a 4-month period of May–August during the summer of 2015. Events were first classified into one of four types based on apparent formation mechanisms and location relative to any low-level jet. A climatology of each of the four types was performed focusing on general spatial tendencies over a large Great Plains ...