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Articles 1 - 13 of 13
Full-Text Articles in Glaciology
Toward The Significance Of Crevasse Orientation In Low And High Crevassed Regions On The Kennicott Glacier, Alaska, Usa, Claire A. Sturm
Toward The Significance Of Crevasse Orientation In Low And High Crevassed Regions On The Kennicott Glacier, Alaska, Usa, Claire A. Sturm
DePaul Discoveries
Supraglacial landforms serve as potential indicators of underlying bedrock morphology and glacier dynamics. The distribution and morphology of crevasses are closely associated with stress fields and ice-flow regimes, representing processes of stable glaciers, in contrast to their reduced occurrence in stagnant or receding ice masses. The orientation and density of crevasses influence a glacier’s ability to absorb solar energy, as they facilitate movement of meltwater down to subglacial rivers. Beyond the meltwater acting as a lubricant for basal sliding, the slope of the bedrock further impacts the local velocity and ice deformation of a glacier. The study of ice-fracturing mechanics …
Geomorphology Of Icy Debris Fans: Delivery Of Ice And Sediment To Valley Glaciers Decoupled From Icecaps, R. Craig Kochel, Jeffrey M. Trop, Robert W. Jacob
Geomorphology Of Icy Debris Fans: Delivery Of Ice And Sediment To Valley Glaciers Decoupled From Icecaps, R. Craig Kochel, Jeffrey M. Trop, Robert W. Jacob
Faculty Journal Articles
The pace and volume of mass flow processes contributing ice and sediment to icy debris fans (IDFs) were documented at sites in Alaska and New Zealand by integrating field observations, drone and time-lapse imagery, ground penetrating radar, and terrestrial laser scanning. Largely unstudied, IDFs are supraglacial landforms at the mouths of bedrock catchments between valley glaciers and icecaps. Time-lapse imagery recorded 300–2300 events reaching 15 fans during intervals from nine months to two years. Field observations noted hundreds of deposits trapped within catchments weekly that were later remobilized onto fans. Deposits were mapped on images taken three to four times …
Assessment Of Nasa Airborne Laser Altimetry Data Using Ground-Based Gps Data Near Summit Station, Greenland, Kelly M. Brunt, Robert L. Hawley, Eric R. Lutz, Michael Studinger
Assessment Of Nasa Airborne Laser Altimetry Data Using Ground-Based Gps Data Near Summit Station, Greenland, Kelly M. Brunt, Robert L. Hawley, Eric R. Lutz, Michael Studinger
Dartmouth Scholarship
A series of NASA airborne lidars have been used in support of satellite laser altimetry missions. These airborne laser altimeters have been deployed for satellite instrument development, for spaceborne data validation, and to bridge the data gap between satellite missions. We used data from ground-based Global Positioning System (GPS) surveys of an 11 km long track near Summit Station, Greenland, to assess the surface–elevation bias and measurement precision of three airborne laser altimeters including the Airborne Topographic Mapper (ATM), the Land, Vegetation, and Ice Sensor (LVIS), and the Multiple Altimeter Beam Experimental Lidar (MABEL). Ground-based GPS data from the monthly …
Greenland Subglacial Drainage Evolution Regulated By Weakly Connected Regions Of The Bed, Matthew J. Hoffman, Lauren C. Andrews, Stephen A. Price, Ginny A. Catania, Thomas A. Neumann, Martin P. Luthi, Jason Gulley, Claudia Ryser, Robert L. Hawley, Blaine Morris
Greenland Subglacial Drainage Evolution Regulated By Weakly Connected Regions Of The Bed, Matthew J. Hoffman, Lauren C. Andrews, Stephen A. Price, Ginny A. Catania, Thomas A. Neumann, Martin P. Luthi, Jason Gulley, Claudia Ryser, Robert L. Hawley, Blaine Morris
Dartmouth Scholarship
Penetration of surface meltwater to the bed of the Greenland Ice Sheet each summer causes an initial increase in ice speed due to elevated basal water pressure, followed by slowdown in late summer that continues into fall and winter. While this seasonal pattern is commonly explained by an evolution of the subglacial drainage system from an inefficient distributed to efficient channelized configuration, mounting evidence indicates that subglacial channels are unable to explain important aspects of hydrodynamic coupling in late summer and fall. Here we use numerical models of subglacial drainage and ice flow to show that limited, gradual leakage of …
Optimized Method For Black Carbon Analysis In Ice And Snow Using The Single Particle Soot Photometer, I. A. Wendl, James A. Menking, R. Färber, M. Gysel, Susan D. Kaspari, M. J. G. Laborde, M. Schwikowski
Optimized Method For Black Carbon Analysis In Ice And Snow Using The Single Particle Soot Photometer, I. A. Wendl, James A. Menking, R. Färber, M. Gysel, Susan D. Kaspari, M. J. G. Laborde, M. Schwikowski
All Faculty Scholarship for the College of the Sciences
In this study we attempt to optimize the method for measuring black carbon (BC) in snow and ice using a Single Particle Soot Photometer (SP2). Beside the previously applied ultrasonic (CETAC) and Collison-type nebulizers we introduce a jet (Apex Q) nebulizer to aerosolize the aqueous sample for SP2 analysis. Both CETAC and Apex Q require small sample volumes (a few milliliters) which makes them suitable for ice core analysis. The Apex Q shows the least size-dependent nebulizing efficiency in the BC particle diameter range of 100–1000 nm. The CETAC has the advantage that air and liquid flows can be monitored …
Seasonal And Elevational Variations Of Black Carbon And Dust In Snow And Ice In The Solu-Khumbu, Nepal And Estimated Radiative Forcings, Susan Kaspari, T. H. Painter, M. Gysel, S. M. Skiles, M. Schwikowski
Seasonal And Elevational Variations Of Black Carbon And Dust In Snow And Ice In The Solu-Khumbu, Nepal And Estimated Radiative Forcings, Susan Kaspari, T. H. Painter, M. Gysel, S. M. Skiles, M. Schwikowski
All Faculty Scholarship for the College of the Sciences
Black carbon (BC) and dust deposited on snow and glacier surfaces can reduce the surface albedo, accelerate snow and ice melt, and trigger albedo feedback. Assessing BC and dust concentrations in snow and ice in the Himalaya is of interest because this region borders large BC and dust sources, and seasonal snow and glacier ice in this region are an important source of water resources. Snow and ice samples were collected from crevasse profiles and snow pits at elevations between 5400 and 6400 m a.s.l. from Mera glacier located in the Solu-Khumbu region of Nepal during spring and fall 2009, …
High Altitude Himalayan Climate Inferred From Glacial Ice Flux, Joel T. Harper, Neil Humphrey
High Altitude Himalayan Climate Inferred From Glacial Ice Flux, Joel T. Harper, Neil Humphrey
Geosciences Faculty Publications
Glaciological processes are modeled to investigate precipitation patterns and the resulting mass flux of snow and ice across Himalayan topography. Our model tracks the accumulation and ablation of snow and ice and the transport of snow and ice across the topography by glacier motion. We investigate high elevation precipitation on the Annapurna Massif by comparing the existing ice cover with model-simulated glaciers produced by a suite of different precipitation scenarios. Our results suggest that precipitation reaches a maximum level well below the elevation of the highest peaks. Further, essentially no snow accumulates on the topography above an elevation of 6200–6300 …
Lead Isotopes And Selected Metals In Ice From Law Dome, Antarctica, K. J. R. Rosman, W. Chisholm, C. F. Boutron, S. Hong, R. Edwards, Vin Morgan, Peter N. Sedwick
Lead Isotopes And Selected Metals In Ice From Law Dome, Antarctica, K. J. R. Rosman, W. Chisholm, C. F. Boutron, S. Hong, R. Edwards, Vin Morgan, Peter N. Sedwick
OES Faculty Publications
The isotopic composition. of Pb and the concentrations of Pb, Ba and Bi were measured in selected ice-core samples from Law Dome, East Antarctica, to a depth of 1196 m. The range of concentrations found in decontaminated ice was 0.03-1.5 pg g-1 for Pb, 0.9-6.1 pg g-1 for Ba and 0.4-17 fg g-1 for Bi, excluding the deepest sample which contained ∼1 ppm of rock dust. The abundances of all four stable lead isotopes were measured and gave 206Pb/207Pb ratios ≤ ∼1.23. A value of 208Pb/207Pb = 2.78 was measured in …
On The Strain-Rate Sensitivity Of Columnar Ice, M. E. Manley, E. M. Schulson
On The Strain-Rate Sensitivity Of Columnar Ice, M. E. Manley, E. M. Schulson
Dartmouth Scholarship
A power law relation between stress and strain rate of the form σ ∝ ε̇1/n was used to describe the response to strain rate of S1 ice loaded across the columns at -10°C. The rate exponent, n, decreased with increasing strain from about 4.6 at an observed peak on the load displacement curve to approximately 2.6 at a shortening of 2%. Analysis of these results and of the results of other authors on different forms of ice deformed at the same temperature suggests that the power law exponent, n, is proportional to Fc/Fg. The parameter Fc/Fg is the far-field basal …
Across-Column Cracks And Axial Splits In S2 Saline Ice Under Compression, E. M. Schulson, S. Qi, J. S. Melton, E. T. Gratz
Across-Column Cracks And Axial Splits In S2 Saline Ice Under Compression, E. M. Schulson, S. Qi, J. S. Melton, E. T. Gratz
Dartmouth Scholarship
Experiments on plate-like specimens have established that across-column cracks from within S2 (columnar) salt-water ice when compressed uniaxially along a direction inclined to the long axis of the grains. Wing cracks initiate from the across-column cracks and lengthen into axial splits when the ice is rapidly deformed; correspondingly; the macroscopic behavior changes from ductile to brittle. The across-column cracking is attributed to grain-boundary sliding, and the splitting to the suppression of crack-tip creep.
Ductile Saline Ice, G. A. Kuehn, E. M. Schulson
Ductile Saline Ice, G. A. Kuehn, E. M. Schulson
Dartmouth Scholarship
Experiments have shown that tensile ductility of about 5% or more can be imparted to columnar, saline ice by pre-compressing the material by about 3.5%. This effect is similar to that observed in granular, fresh-water ice and is attributed to the operation of both dislocation creep and diffusion creep within that part of the matrix which recrystallized during the pre-compressive deformation.
Brittle Compressive Failure Of Salt-Water Columnar Ice Under Biaxial Loading, T. R. Smith, E. M. Schulson
Brittle Compressive Failure Of Salt-Water Columnar Ice Under Biaxial Loading, T. R. Smith, E. M. Schulson
Dartmouth Scholarship
The brittle failure of saline columnar ice was investigated under biaxial compression at and −10° and −40°C over the range 0 ≤ R A < 1 where R A is the ratio of the intermediate to major principal compressive stress. The major principal stress and the intermediate (confining) stress were orthogonal to the columnar axes (type-A confinement); both stresses and the c-axes of the grains were co-planar. The results confirm earlier work by Hausier (1981) and Timco and Frederking (1983, 1986) on saline ice and follow similar behavior to fresh-water columnar ice found by Smith and Schulson (1993) and Frederking (1977). Failure stress and failure mode are sensitive to the confinement and two regimes of behavior are found: the failure stress first rapidly increases with R A in the range 0 ≤ R A < R T and then tends to decrease for R A > R t. The transition stress ratio, R t changes from ≈0.2 at −10°C to ≈0.1 at −40°C. The failure mode changes from axial splitting to shear faulting in the loading plane for 0 < R A < R t. Above R t failure changes to a combined mode of splitting across the columns and shear faulting out of the loading plane. The failure-stress envelope is of a truncated Coulomb-type. Damage studies show wing cracks and local fragmentation of grains involving the brine pockets. The results are explained in terms of Coulombic sliding and Hertzian crack mechanics.
The Effect Of The Specimen–Platen Interface On Internal Cracking And Brittle Fracture Of Ice Under Compression: High-Speed Photography, E. M. Schulson, M. C. Gies, G. J. Lasonde, W. A. Nixon
The Effect Of The Specimen–Platen Interface On Internal Cracking And Brittle Fracture Of Ice Under Compression: High-Speed Photography, E. M. Schulson, M. C. Gies, G. J. Lasonde, W. A. Nixon
Dartmouth Scholarship
Uniaxial compression experiments at –10°C at 10−3s−1 on fresh-water, granular ice have established through the use of high-speed photography that internal cracks nucleate preferentially away from the ice/platen (i/p) interface under conditions of i/p contraint, but near the interface under conditions of i/p expansion. Under conditions of little i/p interaction, cracks nucleate more or less randomly throughout the specimen. Correspondingly, the brittle-fracture strength decreases as the i/p interaction changes from compressive to tensile. These effects are explained in terms of the spatial variation of the maximum shear stress and the crack density.