Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 12 of 12
Full-Text Articles in Physical Sciences and Mathematics
Ice Elevation Near The West Antarctic Ice Sheet Divide During The Last Glaciation, Robert P. Ackert Jr., Sujoy Mukhopadhyay, Byron R. Parizek, Harold W. Borns Jr.
Ice Elevation Near The West Antarctic Ice Sheet Divide During The Last Glaciation, Robert P. Ackert Jr., Sujoy Mukhopadhyay, Byron R. Parizek, Harold W. Borns Jr.
Earth Science Faculty Scholarship
Interior ice elevations of the West Antarctic Ice Sheet (WAIS) during the last glaciation, which can serve as benchmarks for ice-sheet models, are largely unconstrained. Here we report past ice elevation data from the Ohio Range, located near the WAIS divide and the onset region of the Mercer Ice Stream. Cosmogenic exposure ages of glacial erratics that record a WAIS highstand similar to 125 m above the present surface date to similar to 11.5 ka. The deglacial chronology prohibits an interior WAIS contribution to meltwater pulse 1A. Our observational data of ice elevation changes compare well with predictions of a …
Elastic Uplift In Southeast Greenland Due To Rapid Ice Mass Loss, Shfaqat A. Khan, John Wahr, Leigh A. Stearns, Gordon S. Hamilton, Tonie Van Dam, Kristine M. Larson, Olivier Francis
Elastic Uplift In Southeast Greenland Due To Rapid Ice Mass Loss, Shfaqat A. Khan, John Wahr, Leigh A. Stearns, Gordon S. Hamilton, Tonie Van Dam, Kristine M. Larson, Olivier Francis
Earth Science Faculty Scholarship
The rapid unloading of ice from the southeastern sector of the Greenland ice sheet between 2001 and 2006 caused an elastic uplift of similar to 35 mm at a GPS site in Kulusuk. Most of the uplift results from ice dynamic-induced volume losses on two nearby outlet glaciers. Volume loss from Helheim Glacier, calculated from sequential digital elevation models, contributes about similar to 16 mm of the observed uplift, with an additional similar to 5 mm from volume loss of Kangerdlugssuaq Glacier. The remaining uplift signal is attributed to significant melt-induced ice volume loss from the ice sheet margin along …
Reduction In Northward Incursions Of The South Asian Monsoon Since ~1400 Ad Inferred From A Mt. Everest Ice Core, Susan D. Kaspari, Paul Andrew Mayewski, Shichang Kang, Sharon B. Sneed, Shugui Hou, Roger Hooke, Karl J. Kreutz, D. Introne, M. Handley, Kirk A. Maasch, Dahe Qin, J. Ren
Reduction In Northward Incursions Of The South Asian Monsoon Since ~1400 Ad Inferred From A Mt. Everest Ice Core, Susan D. Kaspari, Paul Andrew Mayewski, Shichang Kang, Sharon B. Sneed, Shugui Hou, Roger Hooke, Karl J. Kreutz, D. Introne, M. Handley, Kirk A. Maasch, Dahe Qin, J. Ren
Earth Science Faculty Scholarship
A highly resolved Mt. Everest ice core reveals a decrease in marine and increase in continental air masses related to relatively high summer surface pressure over Mongolia, and reduction in northward incursions of the summer South Asian monsoon since similar to 1400 AD. Previously published proxy records from lower sites south of the Himalayas indicate strengthening of the monsoon since this time. These regional differences are consistent with a south north seesaw in convective activity in the Asian monsoon region, and reflect a southward shift in the mean summer position of the monsoon trough since similar to 1400 AD. The …
Modeling Englacial Radar Attenuation At Siple Dome, West Antarctica, Using Ice Chemistry And Temperature Data, Joseph A. Macgregor, Dale P. Winebrenner, Howard Conway, Kenichi Matsuoka, Paul Andrew Mayewski, Gary D. Clow
Modeling Englacial Radar Attenuation At Siple Dome, West Antarctica, Using Ice Chemistry And Temperature Data, Joseph A. Macgregor, Dale P. Winebrenner, Howard Conway, Kenichi Matsuoka, Paul Andrew Mayewski, Gary D. Clow
Earth Science Faculty Scholarship
The radar reflectivity of an ice-sheet bed is a primary measurement for discriminating between thawed and frozen beds. Uncertainty in englacial radar attenuation and its spatial variation introduces corresponding uncertainty in estimates of basal reflectivity. Radar attenuation is proportional to ice conductivity, which depends on the concentrations of acid and sea-salt chloride and the temperature of the ice. We synthesize published conductivity measurements to specify an ice-conductivity model and find that some of the dielectric properties of ice at radar frequencies are not yet well constrained. Using depth profiles of ice-core chemistry and borehole temperature and an average of the …
Experimental Determination Of Salinity, Temperature, Growth, And Metabolic Effects On Shell Isotope Chemistry Of Mytilus Edulis Collected From Maine And Greenland, Alan D. Wanamaker Jr., Karl J. Kreutz, Harold W. Borns Jr., Douglas S. Introne, Scott Feindel, Svend Funder, Paul D. Rawson, Bruce J. Barber
Experimental Determination Of Salinity, Temperature, Growth, And Metabolic Effects On Shell Isotope Chemistry Of Mytilus Edulis Collected From Maine And Greenland, Alan D. Wanamaker Jr., Karl J. Kreutz, Harold W. Borns Jr., Douglas S. Introne, Scott Feindel, Svend Funder, Paul D. Rawson, Bruce J. Barber
Earth Science Faculty Scholarship
To study the effects of temperature, salinity, and life processes (growth rates, size, metabolic effects, and physiological/ genetic effects) on newly precipitated bivalve carbonate, we quantified shell isotopic chemistry of adult and juvenile animals of the intertidal bivalve Mytilus edulis (Blue mussel) collected alive from western Greenland and the central Gulf of Maine and cultured them under controlled conditions. Data for juvenile and adult M. edulis bivalves cultured in this study, and previously by Wanamaker et al. (2006), yielded statistically identical paleotemperature relationships. On the basis of these experiments we have developed a species-specific paleotemperature equation for the bivalve M. …
Ice Core Paleovolcanic Records From The St. Elias Mountains, Yukon, Canada, Kaplan Yalcin, Cameron P. Wake, Karl J. Kreutz, Mark S. Germani, Sallie I. Whitlow
Ice Core Paleovolcanic Records From The St. Elias Mountains, Yukon, Canada, Kaplan Yalcin, Cameron P. Wake, Karl J. Kreutz, Mark S. Germani, Sallie I. Whitlow
Earth Science Faculty Scholarship
We previously reported a record of regionally significant volcanic eruptions in the North Pacific using an ice core from Eclipse Icefield (St. Elias Mountains, Yukon, Canada). The acquisition of two new ice cores from Eclipse Icefield, along with the previously available Eclipse Icefield and Mount Logan Northwest Col ice cores, allows us to extend our record of North Pacific volcanism to 550 years before present using a suite of four ice cores spanning an elevation range of 3 - 5 km. Comparison of volcanic sulfate flux records demonstrates that the results are highly reproducible, especially for the largest eruptions such …
In Situ Monitoring Of Free-Phase Gas Accumulation And Release In Peatlands Using Ground Penetrating Radar (Gpr), Xavier Comas, Lee Slater, Andrew S. Reeve
In Situ Monitoring Of Free-Phase Gas Accumulation And Release In Peatlands Using Ground Penetrating Radar (Gpr), Xavier Comas, Lee Slater, Andrew S. Reeve
Earth Science Faculty Scholarship
We tested a set of surface common mid-point (CMP) ground penetrating radar (GPR) surveys combined with elevation rods ( to monitor surface deformation) and gas flux measurements to investigate in-situ biogenic gas dynamics and ebullition events in a northern peatland ( raised bog). The main findings are: ( 1) changes in the two-way travel time from the surface to prominent reflectors allow estimation of average gas contents and evolution of free-phase gas (FPG); ( 2) peat surface deformation and gas flux measurements are strongly consistent with GPR estimated changes in FPG content over time; ( 3) rapid decreases in atmospheric …
Rapid Volume Loss From Two East Greenland Outlet Glaciers Quantified Using Repeat Stereo Satellite Imagery, Leigh A. Stearns, Gordon S. Hamilton
Rapid Volume Loss From Two East Greenland Outlet Glaciers Quantified Using Repeat Stereo Satellite Imagery, Leigh A. Stearns, Gordon S. Hamilton
Earth Science Faculty Scholarship
The coastal portions of Kangerdlugssuaq and Helheim glaciers in southeast Greenland lost at least 51 +/- 8 km(-3) yr(-1) of ice between 2001-2006 due to thinning and retreat, according to an analysis of sequential digital elevation models (DEMs) derived from stereo ASTER satellite imagery. The dominant contribution to this ice loss was dynamic thinning caused by the acceleration in flow of both glaciers. Peak rates of change, including thinning rates of similar to 90 m yr(-1), coincided with the rapid increases in flow speed. Extrapolation of the measured data to the ice divides yields an estimated combined catchment volume loss …
Evolution Of Melt Pond Volume On The Surface Of The Greenland Ice Sheet, W. A. Sneed, Gordon S. Hamilton
Evolution Of Melt Pond Volume On The Surface Of The Greenland Ice Sheet, W. A. Sneed, Gordon S. Hamilton
Earth Science Faculty Scholarship
The presence of surface meltwater on ice caps and ice sheets is an important glaciological and climatological characteristic. We describe an algorithm for estimating the depth and hence volume of surface melt ponds using multispectral ASTER satellite imagery. The method relies on reasonable assumptions about the albedo of the bottom surface of the ponds and the optical attenuation characteristics of the ponded meltwater. We apply the technique to sequences of satellite imagery acquired over the western margin of the Greenland Ice Sheet to derive changes in melt pond extent and volume during the period 2001 - 2004. Results show large …
A Coastal Transect Of Mcmurdo Dry Valleys (Antarctica) Snow And Firn: Marine And Terrestrial Influences On Glaciochemistry, B. R. Williamson, Karl J. Kreutz, Paul Andrew Mayewski, N. A.N. Bertler, Sharon B. Sneed, M. Handley, D. Introne
A Coastal Transect Of Mcmurdo Dry Valleys (Antarctica) Snow And Firn: Marine And Terrestrial Influences On Glaciochemistry, B. R. Williamson, Karl J. Kreutz, Paul Andrew Mayewski, N. A.N. Bertler, Sharon B. Sneed, M. Handley, D. Introne
Earth Science Faculty Scholarship
Samples of snow and firn from accumulation zones on Clark, Commonwealth, Blue and Victoria Upper Glaciers in the McMurdo Dry Valleys (similar to 77-78 degrees S, 161-164 degrees E), Antarctica, are evaluated chemically and isotopically to determine the relative importance of local (site-specific) factors vs regional-scale influences in defining glaciochemistry. Spatial variation in snow and firn chemistry confirms documented trends within individual valleys regarding major-ion deposition relative to elevation and to distance from the coast. Sodium and methylsulfonate (MS-), for example, follow a decreasing gradient with distance from the coast along the axis of Victoria Valley (350-119 mu gL(-1) for …
Summer Temperature Trend Over The Past Two Millennia Using Air Content In Himalayan Ice, S. Hou, J. Chappellaz, J. Jouzel, P. C. Chu, V. Masson-Delmotte, Dahe Qin, D. Raynaud, Paul Andrew Mayewski, V. Y. Lipenkov, Shichang Kang
Summer Temperature Trend Over The Past Two Millennia Using Air Content In Himalayan Ice, S. Hou, J. Chappellaz, J. Jouzel, P. C. Chu, V. Masson-Delmotte, Dahe Qin, D. Raynaud, Paul Andrew Mayewski, V. Y. Lipenkov, Shichang Kang
Earth Science Faculty Scholarship
Two Himalayan ice cores display a factor-two decreasing trend of air content over the past two millennia, in contrast to the relatively stable values in Greenland and Antarctica ice cores over the same period. Because the air content can be related with the relative frequency and intensity of melt phenomena, its variations along the Himalayan ice cores provide an indication of summer temperature trend. Our reconstruction point toward an unprecedented warming trend in the 20th century but does not depict the usual trends associated with "Medieval Warm Period" (MWP), or "Little Ice Age" (LIA).
Thermal Conditions At The Bed Of The Laurentide Ice Sheet In Maine During Deglaciation: Implications For Esker Formation, Roger Hooke, James Fastook
Thermal Conditions At The Bed Of The Laurentide Ice Sheet In Maine During Deglaciation: Implications For Esker Formation, Roger Hooke, James Fastook
Earth Science Faculty Scholarship
The University of Maine Ice Sheet Model was used to study basal conditions during retreat of the Laurentide ice sheet in Maine. Within 150 km of the margin, basal melt rates average similar to 5 mm a(-1) during retreat. They decline over the next 100km, so areas of frozen bed develop in northern Maine during retreat. By integrating the melt rate over the drainage area typically subtended by an esker, we obtained a discharge at the margin of similar to 1.2 m(3) s(-1). While such a discharge could have moved the material in the Katahdin esker, it was likely too …