Winter drainage of surface lakes on the Greenland Ice Sheet from Sentinel-1 SAR Imagery
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 re...
| Main Authors: | , |
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| Format: | Text |
| Language: | English |
| Published: |
2020
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| Subjects: | |
| Online Access: | https://doi.org/10.5194/tc-2020-70 https://tc.copernicus.org/preprints/tc-2020-70/ |
| Summary: | 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 km 3 . 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 km 3 to 0.049 km 3 . The findings show that background winter ice motion can trigger rapid lake drainage, which may have important implications for subglacial hydrology and biogeochemical processes. |
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