Links between acceleration, melting, and supraglacial lake drainage at the western Greenland Ice Sheet
Abstract
Observations in west Greenland suggest surface meltwater drainage through kilometer-thick ice can dramatically increase summer velocity, raising concerns about a positive feedback between warming climate and ice sheet mass loss. Using a transect of nine GPS stations spanning 45 km and covering an entire melt season with high temporal resolution, we confirm that ice sheet acceleration is widespread and closely linked to surface melt, showing a similar seasonal and diurnal pattern. Large, abrupt increases in velocity associated with catastrophic drainage of supraglacial lakes appear to be rare, despite the filling and draining of dozens of lakes within the study area. In only a few cases we identify speedup events inferred to result from rapid lake drainage. These events are not coincident with meltwater production, and some include surface elevation change. We hypothesize that most lakes drain slowly via supraglacial streams to pre-existing crevasses or moulins, as opposed to draining catastrophically through local hydrofracturing. In 2007, a high-melt summer, we observe a speedup of 50% up to the equilibrium line lasting approximatley a month, caused by what appears to be widespread sliding. The subglacial hydrologic system of the ice sheet appears to behave similarly to that of alpine glaciers, but because subglacial cavities collapse quickly under thick ice, the ice sheet seems to maintain high basal water pressures and sliding throughout summer whenever surface melt occurs, rather than a single spring speedup. Reorganization of the basal hydrologic system during summer leads to autumn velocities that are slower than winter and highly variable temporally.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.C23B0619H
- Keywords:
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- 0726 CRYOSPHERE / Ice sheets;
- 0740 CRYOSPHERE / Snowmelt;
- 0758 CRYOSPHERE / Remote sensing;
- 0774 CRYOSPHERE / Dynamics