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Full-Text Articles in Glaciology
Modeling And Measuring Water Level Fluctuations In The Greenland Ice Sheet: How Moulin Life Cycle And Shape Can Inform Us On The Subglacial Drainage System., Celia Trunz
Graduate Theses and Dissertations
In the ablation zone of land terminating sectors of the Greenland Ice Sheet (GrIS), water pressures at the bed control ice motion variability on diurnal and seasonal timescales. During the melt season, large volumes of surface meltwater access the ice-bed interface through moulins.Moulins are large vertical shafts that connect the supraglacial and subglacial drainage systems. Moulins form when a crevasse intersects a surface meltwater source that can drive hydrofracture to the bed of the ice sheet. Upon reaching the bed, meltwater can establish and sustain an efficient, channelized drainage system. Due to the technical impossibility of physically exploring underwater passages …
Sustained High Basal Motion Of The Greenland Ice Sheet Revealed By Borehole Deformation, Claudia Ryser, Martin P. Lüthi, Lauren C. Andrews, Matthew J. Hoffman, Ginny A. Catania, Robert L. Hawley
Sustained High Basal Motion Of The Greenland Ice Sheet Revealed By Borehole Deformation, Claudia Ryser, Martin P. Lüthi, Lauren C. Andrews, Matthew J. Hoffman, Ginny A. Catania, Robert L. Hawley
Dartmouth Scholarship
Ice deformation and basal motion characterize the dynamical behavior of the Greenland ice sheet (GrIS). We evaluate the contribution of basal motion from ice deformation measurements in boreholes drilled to the bed at two sites in the western marginal zone of the GrIS. We find a sustained high amount of basal motion contribution to surface velocity of 44–73% in winter, and up to 90% in summer. Measured ice deformation rates show an unexpected variation with depth that can be explained with the help of an ice-flow model as a consequence of stress transfer from slippery to sticky areas. This effect …
Using Airborne Ku-Band Altimeter Waveforms To Investigate Winter Accumulation And Glacier Facies On Austfonna, Svalbard, Robert L. Hawley, Ola Brandt, Thorben Dunse, Jon Ove Hagen, Veit Helm, Jack Kohler, Kirsty Langley, Eirik Malnes, Kjell-Arild Hogda
Using Airborne Ku-Band Altimeter Waveforms To Investigate Winter Accumulation And Glacier Facies On Austfonna, Svalbard, Robert L. Hawley, Ola Brandt, Thorben Dunse, Jon Ove Hagen, Veit Helm, Jack Kohler, Kirsty Langley, Eirik Malnes, Kjell-Arild Hogda
Dartmouth Scholarship
Winter balance is an important metric for assessing the change on glaciers and ice caps, yet measuring it using ground-based techniques can be challenging. We use the European Space Agency prototype Airborne SAR/Interferometric Radar Altimeter System (ASIRAS) to extract snow depths from the received altimeter waveforms over Austfonna ice cap, Svalbard. Additionally, we attempt to distinguish the long-term firn area from other glacier facies. We validate our results using snow depth and glacier facies characterizations determined from ground-based radar profiles, snow pits and a multi-look satellite synthetic aperture radar image. We show that the depth of the winter snowpack can …
Glacimarine Sedimentation Processes At Kronebreen And Kongsvegen, Svalbard, Laura M. Kehrl, Robert L. Hawley, Ross D. Powell, Julie Brigham-Grette
Glacimarine Sedimentation Processes At Kronebreen And Kongsvegen, Svalbard, Laura M. Kehrl, Robert L. Hawley, Ross D. Powell, Julie Brigham-Grette
Dartmouth Scholarship
Tidewater glaciers deposit sediment at their terminus, thereby reducing the relative water depth. Reduced water depth can lead to increased glacier stability through decreased rates of iceberg calving, glacier thinning and submarine melting. Here we investigate sedimentation processes at the termini of Kronebreen and Kongsvegen, Svalbard. We mapped the fjord floor bathymetry in August 2009 and calculate sedimentation rates based on our bathymetry and that from a similar study in 2005. A grounding-line fan is developing near the current position of the subglacial stream. An older, abandoned grounding-line fan that likely formed between ~1987 and 2001 is degrading near the …
Microstructural Evolution Of Fine-Grained Layers Through The Firn Column At Summit, Greenland, R. Lomonaco, M. Albert, I. Baker
Microstructural Evolution Of Fine-Grained Layers Through The Firn Column At Summit, Greenland, R. Lomonaco, M. Albert, I. Baker
Dartmouth Scholarship
We present a microstructural characterization of fine-grained layers from the top 90 m of firn from Summit, Greenland, performed using a combination of scanning electron microscopy techniques including secondary electron imaging, energy-dispersive spectroscopy and electron backscattered patterns, and X-ray microcomputed tomography. The impurities in the firn, both soluble impurities and dust particles, were found largely in the grain interiors. Both c- and a-axis pole figures do not show strong evidence of a preferred orientation of the grains even at the bottom of the firn column. The firn structure became increasingly anisotropic with vertical alignment in the top 3 m, probably …
A New Technique For Firn Grain-Size Measurement Using Sem Image Analysis, N.E. Spaulding, D.A. Meese, I. Baker, P.A. Mayewski
A New Technique For Firn Grain-Size Measurement Using Sem Image Analysis, N.E. Spaulding, D.A. Meese, I. Baker, P.A. Mayewski
Dartmouth Scholarship
Firn microstructure is accurately characterized using images obtained from scanning electron microscopy (SEM). Visibly etched grain boundaries within images are used to create a skeleton outline of the microstructure. A pixel-counting utility is applied to the outline to determine grain area. Firn grain sizes calculated using the technique described here are compared to those calculated using the techniques of Gow (1969) and Gay and Weiss (1999) on samples of the same material, and are found to be substantially smaller. The differences in grain size between the techniques are attributed to sampling deficiencies (e.g. the inclusion of pore filler in the …
Effects Of Impurities And Their Redistribution During Recrystallization Of Ice Crystals, D. Iliescu, I. Baker
Effects Of Impurities And Their Redistribution During Recrystallization Of Ice Crystals, D. Iliescu, I. Baker
Dartmouth Scholarship
In order to examine the effects of solutes on recrystallization and subsequent grain growth in ice, both doped and undoped ice single crystals were extruded through a 120o equal-channel angular extrusion jig, in order to impart a large shear strain (~1.15). Upon subsequent annealing at –3o C, the original single crystals recrystallized, in most cases to a new single crystal with a different orientation. Increasing the solute concentration (for H2SO4 to ~200–300ppb, and for NaCl, KCl and MgSO4 to >5ppm) was found to significantly retard the growth and possibly, for H2SO4 …
Using Electron Backscatter Diffraction Patterns To Examine Recrystallization In Polar Ice Sheets, Rachel Obbard, Ian Baker, Katherine Sieg
Using Electron Backscatter Diffraction Patterns To Examine Recrystallization In Polar Ice Sheets, Rachel Obbard, Ian Baker, Katherine Sieg
Dartmouth Scholarship
The fabric of polycrystalline ice is typically described using the c-axis orientation alone, but this is insufficient for a full description of grain orientations in this hexagonal material. Electron backscatter diffraction (EBSD) provides full c- and a-axis orientation of individual grains, and is used here to study Greenland Ice Sheet Project 2 (GISP2) ice specimens from depths of 1551, 1642 and 1745 m. Complete orientation data are used to compare nearest-neighbor relationships to overall fabric and to differentiate between recrystallization mechanisms. Changes in orientation between grains and subgrains in GISP2 specimens were correlated with the appearance of grain boundaries on …