Subglacial Outburst Events on the Greenland Ice Sheet: Triggers, Routing and Stored Water Release
Abstract
A clear linkage has been identified between supraglacial lakes draining on the Greenland Ice Sheet and the interaction of this water with the ice sheet bed (Das et al., 2008), with waters emerging at the margin in subglacial outburst events. These give rise to increased electrical conductivity and suspended sediment concentrations in glacial runoff (Bartholomew et al., 2011). The drainage of surface lake waters to the ice sheet bed has an impact on glacier summer speed-up due to lubrication of the bed, and drives the development of a more efficient channelized subglacial drainage system (Sundal et al., 2011; Palmer et al., 2011). In addition, the subsequent interaction of supraglacial waters with the ice sheet bed may alter the subglacial biogeochemical weathering environment, entraining suspended sediment, dissolved ions and nutrients which may be exported in runoff. To date, there has been no attempt to study the detailed hydrochemistry of these subglacial outburst events, which may give clues to water routing, residence times and potential mobilization of subglacially stored waters. Here we combine the study of surface lake drainage events inferred from satellite imagery with the detailed hydrochemical characterization of subglacial outburst event runoff at Leverett Glacier, SW Greenland, and lab-based simulations of subglacial weathering. This enables us to infer mechanisms of surface-to-bed hydrological coupling, subglacial water transport, and to determine whether there is a significant long-term subglacially stored water component to these outburst events. MODIS satellite imagery is used to locate and estimate water volumes of draining supraglacial lakes, and indicates that the timing of lake drainage events correlates with outburst events in three study years (2009, 2010 and 2011). We subsequently go on to calculate the potential volumes of stored water released from beneath this outlet glacier of the Greenland Ice Sheet and to propose potential configurations for the subglacial reservoir(s) of stored water.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.C43C0622B
- Keywords:
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- 0726 CRYOSPHERE / Ice sheets;
- 0746 CRYOSPHERE / Lakes;
- 0793 CRYOSPHERE / Biogeochemistry