Rate-Weakening Drag During Glacier Sliding, 2016 University of Wisconsin-Madison
Rate-Weakening Drag During Glacier Sliding, Lucas K. Zoet, Neal R. Iverson
Geological and Atmospheric Sciences Publications
Accurately specifying the relationship between basal drag on a hard, rough glacier bed and sliding speed is a long-standing and central challenge in glaciology. Drag on a rigid bed consisting of steps with linear treads inclined upglacier—a good idealization for the bedrock morphology of some hard-bedded glaciers—has been considered in sliding theories but never studied empirically. Balancing forces parallel to step treads indicates that drag should be independent of sliding speed and cavity size and set by the limit-equilibrium condition sometimes called Iken's bound. In this study we used a large ring-shear device to slide ice at ...
Linking In-Situ Data With Remote Sensing To Analyze Tropical Glacier Stability And Retreat In The Cordillera Blanca, Peru, 2016 Western Kentucky University
Linking In-Situ Data With Remote Sensing To Analyze Tropical Glacier Stability And Retreat In The Cordillera Blanca, Peru, Chandler H. Santos
Masters Theses & Specialist Projects
Glaciers are a major source of freshwater around the world, but they are melting at an increased rate due to atmospheric warming resulting from anthropogenic climate change. In addition to temperature increases, light-absorbing particulates on glaciers also are contributing to glacial melt. This research examines how black carbon, released into the air through partial combustion of biofuels, is affecting the surface albedo of glaciers. I also delineate possible sources of black carbon in the Cordillera Blanca region of Peru. Ground data were collected each year from 2011 to 2013 during the local dry season. Effective black carbon (eBC) values were ...
Trajectory Analysis Of Black Carbon In The Arctic Region, 2016 Portland State University
Trajectory Analysis Of Black Carbon In The Arctic Region, Kimberly Gottschalk
PSU McNair Scholars Online Journal
Black carbon (BC) is a troubling particulate. Commonly known as soot, BC forms through the incomplete combustion of fossil fuels, biofuels, and biomass. It has a very low albedo compared to natural particulates making it a very efficient absorber of solar radiation. As BC is deposited on snow and ice, albedo is decreased - enhancing solar heating and increasing meltwater production. With rising air temperatures, melting rates of polar ice are increasing and are being enhanced by BC, leading to accelerated global sea level rise.
This study aimed to document sources and deposition areas of BC in the Arctic. Utilizing HySplit ...
Modeling Debris-Covered Glaciers: Response To Steady Debris Deposition, 2016 University of Colorado Boulder
Modeling Debris-Covered Glaciers: Response To Steady Debris Deposition, Robert S. Anderson, Leif S. Anderson
Geological Sciences Faculty Contributions
Debris-covered glaciers are common in rapidly eroding alpine landscapes. When thicker than a few centimeters, surface debris suppresses melt rates. If continuous debris cover is present, ablation rates can be significantly reduced leading to increases in glacier length. In order to quantify feedbacks in the debris–glacier–climate system, we developed a 2-D long-valley numerical glacier model that includes englacial and supraglacial debris advection. We ran 120 simulations on a linear bed profile in which a hypothetical steady state debris-free glacier responds to a step increase of surface debris deposition. Simulated glaciers advance to steady states in which ice accumulation ...
Short-Term Climate Cycles, Recent Climate Changes, And Volcano-Ice Hazards: Nevado Coropuna, Arequipa, Peru, William Hardy Kochitzky
Student Honors Theses By Year
The glacier body atop Nevado Coropuna Peru is the largest body of ice in the tropics. The surrounding area is home to ~100,000 people and is vital for agricultural production in southern Peru. Not only does the ice cap provide a water resource to Peruvians in the area, but it also poses a potential hazard if the volcano erupts. The location and physiography of Coropuna make it an excellent location to understand local climate over a variety of timescales in the ice and snow. Using 258 Landsat scenes, to measure snow and ice extent at Coropuna since 1980, this ...
Late Holocene Climate And Environmental Reconstruction Derived From The Asian Ice Core Array (Aica), 2016 Climate Change Institution
Late Holocene Climate And Environmental Reconstruction Derived From The Asian Ice Core Array (Aica), Bjorn Grigholm
Electronic Theses and Dissertations
Recent climate change has impacted natural and human systems across the Earth, emphasizing the need for greater understanding of both the existing and changing natural and anthropogenic forcing mechanisms and subsequent responses of the Earth’s climate system. High-resolution, multi-parameter ice core records retrieved and analyzed from two Asian Ice Core Array (AICA) sites, Geladaindong (central Tibetan Plateau) and Inilchek (central Tien Shan) were utilized to reconstruct atmospheric chemical concentrations and composition over the past ~100-500 years, improving the understanding of late Holocene climate and environmental variability in Asia. Both ice cores were analyzed for major and trace elements, major ...
Effects Of Changes In Moisture Source And The Upstream Rainout On Stable Isotopes In Precipitation – A Case Study In Nanjing, Eastern China, Y. Tang, H. Pang, W. Zhang, Y. Li, Shuang-Ye Wu, S. Hou
In the Asian monsoon region, variations in the stable isotopic composition of speleothems have often been attributed to the "amount effect". However, an increasing number of studies suggest that the "amount effect" in local precipitation is insignificant or even non-existent. To explore this issue further, we examined the variability of daily stable isotopic composition (δ18O) in precipitation from September 2011 to November 2014 in Nanjing, eastern China. We found that intra-seasonal variations of δ18O during summer were not significantly correlated with local rainfall amount but could be linked to changes in the moisture source location and rainout processes in the ...
Reconstruction Of The Hirnantian (Late Ordovician) Palaeotopography In The Upper Yangtze Region, 2016 University of Chinese Academy of Sciences
Reconstruction Of The Hirnantian (Late Ordovician) Palaeotopography In The Upper Yangtze Region, Linna Zhang, Junxuan Fan, Qing Chen, Shuang-Ye Wu
Reconstruction of the Hirnantian (Late Ordovician) palaeotopography in South China is important for understanding the distribution pattern of the Hirnantian marine depositional environment. In this study, we reconstructed the Hirnantian palaeotopography in the Upper Yangtze region based on the rankings of the palaeo-water depths, which were inferred according to the lithofacies and biofacies characteristics of the sections. Data from 374 Hirnantian sections were collected and standardized through the online Geobiodiversity Database. The Ordinary Kriging interpolation method in the ArcGIS software was applied to create the continuous surface of the palaeo-water depths, i.e. the Hirnantian palaeotopography. Meanwhile, the line transect ...
The Last Glacial Maximum In Central North Island, New Zealand: Palaeoclimate Inferences From Glacier Modelling, 2016 Victoria University of Wellington
The Last Glacial Maximum In Central North Island, New Zealand: Palaeoclimate Inferences From Glacier Modelling, Shaun. R. Eaves, Andrew N. Mackintosh, Brian M. Anderson, Alice M. Doughty
Open Dartmouth: Faculty Open Access Articles
Quantitative palaeoclimate reconstructions provide data for evaluating the mechanisms of past, natural climate variability. Geometries of former mountain glaciers constrained by moraine mapping afford the opportunity to reconstruct palaeoclimate, due to the close relationship between ice extent and local climate. In this study, we present results from a series of experiments using a 2D coupled energy-balance/ice-flow model that investigate the palaeoclimate significance of Last Glacial Maximum m
oraines within nine catchments in the central North Island, New Zealand. We find that the former ice limits can be simulated when present-day temperatures are reduced by between 4 and 7 ◦C ...
Transition From Contraction To Extension In The Northeastern Basin And Range: New Evidence From The Copper Mountains, Nevada, Jeffrey M. Rahl, Allen J. Mcgrew, Kenneth A. Foland
Allen J. McGrew
New mapping, structural analysis, and 40Ar/39Ar dating reveal an unusually well‐constrained history of Late Eocene extension in the Copper Mountains of the northern Basin and Range province. In this area, the northeast‐trending Copper Creek normal fault juxtaposes a distinctive sequence of metacarbonate and granitoid rocks against a footwall of Upper Precambrian to Lower Cambrian quartzite and phyllite. Correlation of the hanging wall with footwall rocks to the northwest provides an approximate piercing point that requires 8–12 km displacement in an ESE direction. This displaced fault slice is itself bounded above by another normal fault (the Meadow ...
Prevailing Weather Conditions During Summer Seasons Around Gangotri Glacier, 2016 Hydro Tasmania Consulting
Prevailing Weather Conditions During Summer Seasons Around Gangotri Glacier, Pratap Singh, Umesh K. Haritashya, K. S. Ramasastri, Naresh Kumar
Umesh K. Haritashya
Meteorological data collected near the snout of the Gangotri Glacier suggest that the study area receives less rainfall. The average seasonal rainfall is observed to be about 260 mm. The rainfall distribution does not show any monsoon impact. Amount of seasonal rainfall is highly variable (131.4-368.8 mm) from year to year, but, in general, August had the maximum rainfall. A verage daily maximum and minimum temperatures were 14.7 and 4.1°C respectively, whereas average mean temperature was 9.4°C. July was recorded as the warmest month. During daytime, wind speed was four times higher than ...
Multispectral Image Analysis Of Glaciers And Glacier Lakes In The Chugach Mountains, Alaska, 2016 University of Colorado
Multispectral Image Analysis Of Glaciers And Glacier Lakes In The Chugach Mountains, Alaska, Jeffrey Kargel, Matthew Beedle, Andrew Bush, Francisco Carreño, Elena Castellanos, Umesh Haritashya, Gregory Leonard, Javier Lillo, Ivan Lopez, Mark Pleasants, Edward Pollock, David Wolfe
The Chugach Mountains contain the largest nonpolar alpine glaciers in the world and include a wide variety of glacier types: some are land terminating; some calve variously into tidewater, lakes, and rivers; some are heavily debris covered; some are surge-type, whereas others are neither debris covered nor surge type. Nearly all are retreating, thinning, or both, though some rare ones are advancing, and some are thickening at high elevations. To assist the further documentation of changes, we establish an inventory of glaciers in the eastern Chugach Mountains. Several case studies of diverse glacier types showcase remotesensing applications and are used ...
Iceland: Extreme Learning In The Land Of Fire And Ice, 2016 Western Kentucky University Hoffman Institute
Iceland: Extreme Learning In The Land Of Fire And Ice, Jason Polk, Leslie North
WKU Libraries kicked off the spring season of "Far Away Places" with Dr. Jason Polk and Dr. Leslie North, Asstant Professors from the Department of Geography and Geology at WKU, who talked about leading a study abroad group to Iceland in the summer of 2015. WKU Libraries kicks off the spring season of Far Away Places with Jason Polk and Leslie North, Asst. Professors from the Department of Geography and Geology at WKU, who will be talking about leading a study abroad group to Iceland in the summer of 2015. Dr. Polk and Dr. North co-taught this course with faculty ...
Distributed Modeling Of Ablation (1996–2011) And Climate Sensitivity On The Glaciers Of Taylor Valley, Antarctica, 2016 Los Alamos National Laboratory
Distributed Modeling Of Ablation (1996–2011) And Climate Sensitivity On The Glaciers Of Taylor Valley, Antarctica, Matthew J. Hoffman, Andrew G. Fountain, Glen E. Liston
Geology Faculty Publications and Presentations
The McMurdo Dry Valleys of Antarctica host the coldest and driest ecosystem on Earth, which is acutely sensitive to the availability of water coming from glacial runoff. We modeled the spatial variability in ablation and assessed climate sensitivity of the glacier ablation zones using 16 years of meteorological and surface mass-balance observations collected in Taylor Valley. Sublimation was the primary form of mass loss over much of the ablation zones, except for near the termini where melt, primarily below the surface, dominated. Microclimates in ~10 m scale topographic basins generated melt rates up to ten times higher than over smooth ...
Processes Controlling Carbon Cycling In Antarctic Glacier Surface Ecosystems, 2016 Cardiff University
Processes Controlling Carbon Cycling In Antarctic Glacier Surface Ecosystems, Elizabeth A. Bagshaw, Martyn Tranter, Jemma L. Wadham, Andrew G. Fountain, A. Dubnick, S. Fitzsimons
Geology Faculty Publications and Presentations
Glacier surface ecosystems, including cryoconite holes and cryolakes, are significant contributors to regional carbon cycles. Incubation experiments to determine the net production (NEP) of organic matter in cryoconite typically have durations of 6-24 hours, and produce a wide range of results, many of which indicate that the system is net heterotrophic. We employ longer term incubations to examine the temporal variation of NEP in cryoconite from the McMurdo Dry Valleys, Antarctica to examine the effect of sediment disturbance on system production, and to understand processes controlling production over the lifetimes of glacier surface ecosystems. The shorter-term incubations have durations of ...
Estimating Supraglacial Lake Depth In West Greenland Using Landsat 8 And Comparison With Other Multispectral Methods, 2016 University of Colorado Boulder
Estimating Supraglacial Lake Depth In West Greenland Using Landsat 8 And Comparison With Other Multispectral Methods, Allen Pope, T A. Scambos, M Moussavi, M Tedesco, M Willis, D Shean, S Grigsby
University Libraries Open Access Fund Supported Publications
Liquid water stored on the surface of ice sheets and glaciers impacts surface mass balance, ice dynamics, and heat transport. Multispectral remote sensing can be used to detect supraglacial lakes and estimate their depth and area. In this study, we use in situ spectral and bathymetric data to assess lake depth retrieval using the recently launched Landsat 8 Operational Land Imager (OLI). We also extend our analysis to other multispectral sensors to evaluate their performance with similar methods. Digital elevation models derived from WorldView stereo imagery (pre-lake filling and post-drainage) are used to validate spectrally derived depths, combined with a ...
Influence Of Sea Ice On Arctic Precipitation, 2016 Dartmouth College
Influence Of Sea Ice On Arctic Precipitation, Ben G. Kopec, Xiahong Feng, Fred A. Michel, Eric S. Posmentier
Open Dartmouth: Faculty Open Access Articles
Global climate is influenced by the Arctic hydrologic cycle, which is, in part, regulated by sea ice through its control on evaporation and precipitation. However, the quantitative link between precipitation and sea ice extent is poorly constrained. Here we present observational evidence for the response of precipitation to sea ice reduction and assess the sensitivity of the response. Changes in the proportion of moisture sourced from the Arctic with sea ice change in the Canadian Arctic and Greenland Sea regions over the past two decades are inferred from annually averaged deuterium excess (d-excess) measurements from six sites. Other influences on ...
Large Ensemble Modeling Of The Last Deglacial Retreat Of The West Antarctic Ice Sheet: Comparison Of Simple And Advanced Statistical Techniques, 2016 The Pennsylvania State University
Large Ensemble Modeling Of The Last Deglacial Retreat Of The West Antarctic Ice Sheet: Comparison Of Simple And Advanced Statistical Techniques, David Pollard, Won Chang, Murali Haran, Patrick Applegate, Robert Deconto
Geosciences Department Faculty Publication Series
A 3-D hybrid ice-sheet model is applied to the last deglacial retreat of the West Antarctic Ice Sheet over the last ∼ 20 000 yr. A large ensemble of 625 model runs is used to calibrate the model to modern and geologic data, including reconstructed grounding lines, relative sea-level records, elevation–age data and uplift rates, with an aggregate score computed for each run that measures overall model–data misfit. Two types of statistical methods are used to analyze the large-ensemble results: simple averaging weighted by the aggregate score, and more advanced Bayesian techniques involving Gaussian process-based emulation and calibration, and ...
Bering Sea Surface Water Conditions During Marine Isotope Stages 12 To 10 At Navarin Canyon (Iodp Site U1345), 2016 Iowa State University
Bering Sea Surface Water Conditions During Marine Isotope Stages 12 To 10 At Navarin Canyon (Iodp Site U1345), Beth E. Caissie, Julie Brigham-Grette, Mea S. Cook, Elena Colmenero-Hidalgo
Geological and Atmospheric Sciences Publications
Records of past warm periods are essential for understanding interglacial climate system dynamics. Marine Isotope Stage 11 occurred from 425 to 394 ka, when global ice volume was the lowest, sea level was the highest, and terrestrial temperatures were the warmest of the last 500 kyr. Because of its extreme character, this interval has been considered an analog for the next century of climate change. The Bering Sea is ideally situated to record how opening or closing of the Pacific–Arctic Ocean gateway (Bering Strait) impacted primary productivity, sea ice, and sediment transport in the past; however, little is known ...
High-Resolution Ground-Penetrating Radar Profiles Of Perennial Lake Ice In The Mcmurdo Dry Valleys, Antarctica: Horizon Attributes, Unconformities, And Subbottom, 2016 University of Wisconsin - Madison
High-Resolution Ground-Penetrating Radar Profiles Of Perennial Lake Ice In The Mcmurdo Dry Valleys, Antarctica: Horizon Attributes, Unconformities, And Subbottom, Hilary A. Dugan, Steven A. Arcone, Maciej K. Obryk, Peter T. Doran
Geology Faculty Publications and Presentations
Ground-penetrating radar (GPR) is not commonly used to study lake ice, and in general, the ground-based use of radar frequencies greater than 500 MHz in cryosphere geophysics is rare, due to a general interest in deeper stratigraphy and the difficulty of extensive profiling over rough snow surfaces. Our goal was to find further information on the origin of the deposition and formation of intra-ice layers, bottom topography, and subbottom deposits using GPR with pulses centered near 850 MHz on two permanently ice-covered lakes in the Mc- Murdo Dry Valleys, Antarctica. The profiles were obtained using a one-person sled operation over ...