Glaciology Commons^™

Influence Of Regional Precipitation Patterns On Stable Isotopes In Ice Cores From The Central Himalayas, H. Pang, S. Hou, Susan Kaspari, P. A. Mayewski

All Faculty Scholarship for the College of the Sciences

Several ice cores have been recovered from the Dasuopu (DSP) Glacier and the East Rongbuk (ER) Glacier in the central Himalayas since the 1990s. Although the distance between the DSP and the ER ice core drilling sites is only 125 km, the stable isotopic record (18O or D) of the DSP core is interpreted in previous studies as a temperature proxy, while the ER core is interpreted as a precipitation proxy. Thus, the climatological significance of the stable isotopic records of these Himalayan ice cores remains a subject of debate. Based on analysis of regional precipitation patterns over the region, …

Seismic And Geodetic Evidence For Grounding-Line Control Of Whillans Ice Stream Stick-Slip Events, Martin J. Pratt, J. Paul Winberry, Douglas A. Wiens, Sridhar Anandakrishnan, Richard B. Alley

All Faculty Scholarship for the College of the Sciences

The tidally modulated, stick‐slip events of Whillans Ice Stream in West Antarctica produce seismic energy from three locations near the grounding line. Using ice velocity records obtained by combining time series from colocated broadband seismometers and GPS receivers installed on the ice stream during the 2010–2011 and 2011–2012 austral summers, along with far‐field seismic recordings of elastic waves, we locate regions of high rupture velocity and stress drop. These regions, which are analogous to “asperities” in traditional seismic fault studies, are areas of elevated friction at the base of the ice stream. Slip events consistently initiate at one of two …

Plastic Faulting In Saltwater Ice, Narayana Golding, Scott A. Snyder, Erland M. Schulson, Carl E. Renshaw

Dartmouth Scholarship

Compression experiments on laboratory-grown columnar S2 saltwater ice loaded triaxially through proportional loading at T = –20°C at applied strain rates of ε = 10–5–10–1 s–1 demonstrate that plastic (P) faulting is a mode of failure in saltwater ice when rapidly loaded under a high degree of confinement. In terms of microstructure, mechanical behavior and strength, saltwater ice that fails via P-faulting is almost indistinguishable from columnar S2 freshwater ice that fails via P-faulting loaded under the same conditions. The results also demonstrate that saltwater ice loaded rapidly may exhibit yet another mode of failure, in addition to P-faulting, through …

Melt Water Input From The Bering Glacier Watershed Into The Gulf Of Alaska, Edward G. Josberger, Robert Shuchman, Liza K. Jenkins, K. A. Endsley

Michigan Tech Research Institute Publications

The annual runoff from the melting of large glaciers and snow fields along the northern perimeter of the Gulf of Alaska is a critical component of marine physical and biological systems; yet, most of this freshwater is not measured. Here we show estimates of melt for the watershed that contains the largest and longest glacier in North America, the Bering Glacier. The procedure combines in situ observations of snow and ice melt acquired by a long-term monitoring program, multispectral satellite observations, and nearby temperature measurements. The estimated melt is 40 km3 per melt season, ± 3.0 km3, observed over the …

Impact Of Physical Properties And Accumulation Rate On Pore Close-Off In Layered Firn, S. A. Gregory, M. R. Albert, I. Baker

Dartmouth Scholarship

Investigations into the physical characteristics of deep firn near the lock-in zone through pore close-off are needed to improve understanding of ice core records of past atmospheric composition. Specifically, the permeability and microstructure profiles of the firn through the diffusive column influence the entrapment of air into bubbles and thus the ice age–gas age difference. The purpose of this study is to examine the nature of pore closure processes at two polar sites with very different local temperatures and accumulation rates. Density, permeability, and microstructure measurements were made on firn cores from the West Antarctic Ice Sheet (WAIS) Divide, a …

Lithologic Influences On Groundwater Recharge Through Incised Glacial Till From Profile To Regional Scales: Evidence From Glaciated Eastern Nebraska, John L. Gates, Gregory V. Steele, Paolo Nasta, Jozsef Szilagyi

United States Geological Survey: Water Reports and Publications

[1] Variability in sediment hydraulic properties associated with landscape depositional and erosional features can influence groundwater recharge processes by affecting soil-water storage and transmission. This study considers recharge to aquifers underlying river-incised glaciated terrain where the distribution of clay-rich till is largely intact in upland locations but has been removed by alluvial erosion in stream valleys. In a stream-dissected glacial region in eastern Nebraska (Great Plains region of the United States), recharge estimates were developed for nested profile, aquifer, and regional scales using unsaturated zone profile measurements (matric potentials, Cl⁻ and ³H), groundwater tracers (CFC-12 and SF_{6 …}

Weekly Gridded Aquarius L-Band Radiometer/Scatterometer Observations And Salinity Retrievals Over The Polar Regions - Part 1: Product Description, L. Brucker, Emmanuel P. Dinnat, L. S. Koenig

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Passive and active observations at L band (frequency similar to 1.4 GHz) from the Aquarius/SAC-D mission offer new capabilities to study the polar regions. Due to the lack of polar-gridded products, however, applications over the cryosphere have been limited. We present three weekly polar-gridded products of Aquarius data to improve our understanding of L-band observations of ice sheets, sea ice, permafrost, and the polar oceans. Additionally, these products intend to facilitate access to L-band data, and can be used to assist in algorithm developments. Aquarius data at latitudes higher than 50 degrees are averaged and gridded into weekly products of …

Weekly Gridded Aquarius L-Band Radiometer/Scatterometer Observations And Salinity Retrievals Over The Polar Regions - Part 2: Initial Product Analysis, L. Brucker, Emmanuel P. Dinnat, L. S. Koenig

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Following the development and availability of Aquarius weekly polar-gridded products, this study presents the spatial and temporal radiometer and scatterometer observations at L band (frequency similar to 1.4 GHz) over the cryosphere including the Greenland and Antarctic ice sheets, sea ice in both hemispheres, and over sub-Arctic land for monitoring the soil freeze/thaw state. We provide multiple examples of scientific applications for the L-band data over the cryosphere. For example, we show that over the Greenland Ice Sheet, the unusual 2012 melt event lead to an L-band brightness temperature (TB) sustained decrease of similar to 5K at horizontal polarization. Over …

A Data Set Of Worldwide Glacier Length Fluctuations, Paul W. Leclercq, Johannes Oerlemans, Hassan J. Basagic, Christina Bushueva, A. J. Cook, Raymond Le Bris

Geology Faculty Publications and Presentations

Glacier fluctuations contribute to variations in sea level and historical glacier length fluctuations are natural indicators of past climate change. To study these subjects, longterm information of glacier change is needed. In this paper we present a data set of global long-term glacier length fluctuations. The data set is a compilation of available information on changes in glacier length worldwide, including both measured and reconstructed glacier length fluctuations. All 471 length series start before 1950 and cover at least four decades. The longest record starts in 1535, but the majority of time series start after 1850. The number of available …

Reconstruction Of The Hirnantian (Late Ordovician) Palaeotopography In The Upper Yangtze Region, Linna Zhang, Junxuan Fan, Qing Chen, Shuang-Ye Wu

Department of Earth, Environment and Sustainability Faculty Publications

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 analysis …

Tidal Pacing, Skipped Slips And The Slowdown Of Whillans Ice Stream, Antarctica, J. Paul Winberry, Sridhar Anandakrishnan, Richard B. Alley, Douglas A. Wiens, Martin J. Pratt

All Faculty Scholarship for the College of the Sciences

We summarize new observations of the deceleration and stick–slip motion of Whillans Ice Stream (WIS), Antarctica. We refine the location of the large sticky spots that resist motion between slip events, the locations of which are controlled by the patterns of subglacial water flow. Our examination of the long-term velocity time series for the ice stream reveals that the decadal-scale deceleration is not occurring at a steady rate, but varies at the sub-decadal timescale. This unsteady deceleration modulates the temporal evolution of a broad (~50 km across) surface-elevation bulge forming at the junction between the relatively narrow upstream portion of …

Interferometric Swath Processing Of Cryosat Data For Glacial Ice Topography, L. Gray, D. Burgess, L. Copland, R. Cullen, N. Galin, R. Hawley, V. Helm

Dartmouth Scholarship

We have derived digital elevation models (DEMs) over the western part of the Devon Ice Cap in Nunavut, Canada, using "swath processing" of interferometric data collected by Cryosat between February 2011 and January 2012. With the standard ESA (European Space Agency) SARIn (synthetic aperture radar interferometry) level 2 (L2) data product, the interferometric mode is used to map the cross-track position and elevation of the "point-of-closest-approach" (POCA) in sloping glacial terrain. However, in this work we explore the extent to which the phase of the returns in the intermediate L1b product can also be used to map the heights of …

A Ten-Year Record Of Supraglacial Lake Evolution And Rapid Drainage In West Greenland Using An Automated Processing Algorithm For Multispectral Imagery, B. F. Morriss, R. L. Hawley, J. W. Chipman, L. C. Andrews

Dartmouth Scholarship

The rapid drainage of supraglacial lakes introduces large pulses of meltwater to the subglacial environment and creates moulins, surface-to-bed conduits for future melt. Introduction of water to the subglacial system has been shown to affect ice flow, and modeling suggests that variability in water supply and delivery to the subsurface play an important role in the development of the subglacial hydrologic system and its ability to enhance or mitigate ice flow. We developed a fully automated method for tracking meltwater and rapid drainages in large (> 0.125 km²) perennial lakes and applied it to a 10 yr time …

Surficial Geologic Map Of Kings Canyon: Implications For Relatively Slow Stream Incision Rates, Andrew Farris

Natural Resources Management and Environmental Sciences

Most of the Kings River in the Sierra Nevada Mountains of California has responded to regional uplift with rapid incision, creating the deepest canyon in the United States. However, Kings Canyon near Cedar Grove is still a mountainous relict landscape with little evidence of fluvial incision. Mapping took place in the Cedar Grove area of Kings Canyon to assess factors and/or processes causing relatively low stream incision rates in the region during Holocene time. A surficial geologic map was created in the field, along with visual observations of the South Fork of the Kings River and characterization of geologic map …

Glacier Slip And Seismicity Induced By Surface Melt, Peter L. Moore, J. Paul Winberry, Neal R. Iverson, Knut A. Christianson, Sridhar Anandakrishnan, Miriam Jackson, Mark E. Mathison, Denis Cohen

All Faculty Scholarship for the College of the Sciences

Many of the key processes governing fast glacier flow involve interaction between a glacier and its basal hydrological system, which is hidden from direct observation. Passive seismic monitoring has shown promise as a tool for remotely monitoring basal processes, but lack of glacier-bed access prevents clear understanding of the relationships between subglacial processes and corresponding seismic emissions. Here we describe direct measurements of basal hydrology, sliding, and broadband seismicity made in a unique subglacial facility in Norway during the onset of two summer melt seasons. In the most pronounced of these episodes, rapid delivery of surface meltwater to the bed …

Recent Accumulation Variability In Northwest Greenland From Ground-Penetrating Radar And Shallow Cores Along The Greenland Inland Traverse, Robert L. Hawley, Zoe R. Courville, Laura M. Kehrl, Eric R. Lutz, Erich C. Osterberg, Thomas B. Overly, Gifford J. Wong

Dartmouth Scholarship

Accumulation is a key parameter governing the mass balance of the Greenland ice sheet. Several studies have documented the spatial variability of accumulation over wide spatial scales, primarily using point data, remote sensing or modeling. Direct measurements of spatially extensive, detailed profiles of accumulation in Greenland, however, are rare. We used 400 MHz ground-penetrating radar along the 1009 km route of the Greenland Inland Traverse from Thule to Summit during April and May of 2011, to image continuous internal reflecting horizons. We dated these horizons using ice-core chemistry at each end of the traverse. Using density profiles measured along the …

Where To Find 1.5 Million Yr Old Ice For The Ipics "Oldest Ice" Ice Core, H. Fischer, J. Severinghaus, E. Brook, E. Wolff, M. Albert

Dartmouth Scholarship

Abstract. The recovery of a 1.5 million yr long ice core from Antarctica represents a keystone of our understanding of Quaternary climate, the progression of glaciation over this time period and the role of greenhouse gas cycles in this pro- gression. Here we tackle the question of where such ice may still be found in the Antarctic ice sheet. We can show that such old ice is most likely to exist in the plateau area of the East Antarctic ice sheet (EAIS) without stratigraphic distur- bance and should be able to be recovered after careful pre- site selection studies. Based …

Geogram 2013, David J. Keeling Editor, Wku Department Of Geography And Geology

Earth, Environmental, and Atmospheric Sciences Publications

No abstract provided.

Origin And Provenance Of Spherules And Magnetic Grains At The Younger Dryas Boundary, Yingzhe Wu, Mukul Sharma, Malcom A. Lecompte, Mark N. Demitroff, Joshua D. Landis

Dartmouth Scholarship

One or more bolide impacts are hypothesized to have triggered the Younger Dryas cooling at ∼12.9 ka. In support of this hypothesis, varying peak abundances of magnetic grains with iridium and magnetic microspherules have been reported at the Younger Dryas boundary (YDB). We show that bulk sediment and/or magnetic grains/microspherules collected from the YDB sites in Arizona, Michigan, New Mexico, New Jersey, and Ohio have (187)Os/(188)Os ratios ≥1.0, similar to average upper continental crust (= 1.3), indicating a terrestrial origin of osmium (Os) in these samples. In contrast, bulk sediments from YDB sites in Belgium and Pennsylvania exhibit (187)Os/(188)Os ratios <<1.0 and at face value suggest mixing with extraterrestrial Os with (187)Os/(188)Os of ∼0.13. However, the Os concentration in bulk sample and magnetic grains from Belgium is 2.8 pg/g and 15 pg/g, respectively, much lower than that in average upper continental crust (=31 pg/g), indicating no meteoritic contribution. The YDB site in Pennsylvania is remarkable in yielding 2- to 5-mm diameter spherules containing minerals such as suessite (Fe-Ni silicide) that form at temperatures in excess of 2000 °C. Gross texture, mineralogy, and age of the spherules appear consistent with their formation as ejecta from an impact 12.9 ka ago. The (187)Os/(188)Os ratios of the spherules and their leachates are often low, but Os in these objects is likely terrestrially derived. The rare earth element patterns and Sr and Nd isotopes of the spherules indicate that their source lies in 1.5-Ga Quebecia terrain in the Grenville Province of northeastern North America.

Lithic Analysis Of Coyote Canyon Mammoth Site Sediments, Kaitlin M. Hill, George V. Last

STAR Program Research Presentations

The landforms and geologic layers of Southeastern Washington record fascinating, unique geologic events, including repeated catastrophic flooding that occurred during the last Ice Age. These floods left behind many distinctive features, and a variety of fossils. After discovery of mammoth-sized bones in 1999, and confirmation that more bones were still in place in 2008, the Coyote Canyon Mammoth Site near Kennewick, Washington was secured for research, and formal excavation began in 2010.

Previous research suggests that the remains are buried in Ice Age flood deposits, which are overlain by eolian sediments, and those in turn overlain by slope wash. We …