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The Cryosphere An interactive open-access journal of the European Geosciences Union
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Preprints
https://doi.org/10.5194/tc-2020-70
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/tc-2020-70
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  14 May 2020

14 May 2020

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A revised version of this preprint is currently under review for the journal TC.

Winter drainage of surface lakes on the Greenland Ice Sheet from Sentinel-1 SAR Imagery

Corinne Benedek and Ian Willis Corinne Benedek and Ian Willis
  • University of Cambridge, CB2 1ER, UK

Abstract. Surface lakes on the Greenland Ice Sheet play a key role in its surface mass balance, hydrology, and biogeochemistry. They often drain rapidly in the summer via hydrofracture, which immediately delivers lake water to the ice sheet base over timescales of hours to days and then allows meltwater to reach the base for the rest of the summer. Rapid lake drainage, therefore, influences subglacial drainage evolution, water pressures, ice flow, biogeochemical activity, and ultimately the delivery of water, sediments and nutrients to the ocean. It is assumed that rapid lake drainage events are confined to the summer, as this is when all observations to date have been made. Here we develop a method to quantify backscatter changes in satellite radar imagery, which we use to document the drainage of six different lakes during three winters in fast flowing parts of the Greenland Ice Sheet. Analysis of optical imagery from before and after the three winters supports the radar-based evidence for winter lake drainage events and also provides estimates of lake drainage volumes, which range between 0.000046 and 0.0202 km3. For three of the events, optical imagery allows photoclinometry (shape from shading) calculations to be made showing mean vertical collapse of the lake surfaces ranging between 4.04 m and 7.25 m, and drainage volumes of 0.004 km3 to 0.049 km3. The findings show that background winter ice motion can trigger rapid lake drainage, which may have important implications for subglacial hydrology and biogeochemical processes.

Corinne Benedek and Ian Willis

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Corinne Benedek and Ian Willis

Corinne Benedek and Ian Willis

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Latest update: 17 Sep 2020
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Short summary
The surface of the Greenland Ice Sheet contains thousands of surface lakes. These lakes can deliver water through cracks to the ice sheet base and influence the speed of ice flow. Here we look at instances of lakes draining in the middle of winter using the Sentinel-1 radar satellites. Winter draining lakes can help us understand the mechanisms for lake drainages throughout the year and can point to winter movement of water that will impact our understanding of ice sheet hydrology.
The surface of the Greenland Ice Sheet contains thousands of surface lakes. These lakes can...
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