Seasonal variations in Greenland Ice Sheet motion: inland extent and behaviour at higher elevations in a land-terminating transect
Abstract
Land-terminating glaciers in the lower ablation zone of the Greenland Ice Sheet undergo seasonal acceleration when surface generated meltwaters reach the ice-bed interface. It is expected that these waters will access the ice-bed interface further inland in a warmer climate. A key mechanism to allow this is drainage of supraglacial lakes by hydrofracture. However, although the dynamic effect of an individual lake drainage event has been described in detail, it is not clear that the integrated effect of lake drainage will be a widespread and sustained increase in ice velocities at higher elevations. In order to address this, we present ice velocity measurements that capture the full extent of seasonal velocity variations along a transect of GPS receivers at 67 °N in western Greenland from the 2009 melt season. Sites in the lower ablation zone display an increase in annual velocity of about 16 % due to summer velocity variations. Above 800 m elevation the effect is less marked and sites display an acceleration of only 4 - 6 %. Consideration of elevation changes in the GPS records, surface melt rates, and satellite investigations of supraglacial lake drainage, indicates that variations in ice velocity at higher elevations only occur later in the melt season once enough water has collected to penetrate to the ice sheet bed. By this time seasonal melt is diminishing, limiting the effect that this meltwater can have on ice velocities. We suggest that in a warmer climate supraglacial lakes will form and drain earlier in the season and the observed behaviour from the lower ablation zone will become applicable over a wider area. As a result, we predict a positive relationship between dynamic mass loss and atmospheric warming in land-terminating regions of the Greenland Ice Sheet which is controlled by spatial expansion of the ablation zone.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.C23B0620B
- Keywords:
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- 0700 CRYOSPHERE;
- 0726 CRYOSPHERE / Ice sheets;
- 0774 CRYOSPHERE / Dynamics;
- 0776 CRYOSPHERE / Glaciology