Distribution and Evolution of Crevasses Draining the Firn Aquifer in Southeast Greenland Identified with a Ghub Tool
Abstract
In Southeast Greenland, high snowfall rates tend to bury summer meltwater before cold winter temperatures can refreeze it. This gives rise to firn aquifers: vast stores of liquid water located tens of meters beneath the ice-sheet surface. These firn aquifers are thought to drain their water to the ice-sheet bed, but the locations and timing of drainage episodes are currently unknown.
Massively enlarged crevasses at the downstream ends of firn aquifers provide indirect evidence of water drainage to the bed. These crevasses, generally 20-25 meters wide at the ice sheet surface, are detectable in data from the Airborne Topographic Mapper (ATM) that was collected annually by NASA's Operation IceBridge (OIB). We analyzed these data over 2013-2018 using a tool in Ghub, a new online repository of datasets, tools, and supercomputing resources for ice sheet science. Our tool ingests the ATM data, fits local parabolic surfaces, subtracts those from the data, and identifies distinct features in the elevation anomalies. The tool returns the locations, widths, and depths of detected crevasses along all OIB flight lines across a user-defined area. We analyzed the firn aquifer in the Puisortoq region, near the Southern tip of Greenland, to determine the spatial patterns between crevasses and the firn aquifer. The OIB flight lines crossing this region allow us to gather data from multiple downstream locations year to year. We find that wide crevasses are present directly downstream from the firn aquifer boundary along all OIB flight lines studied. The tool identifies some crevasses inside the firn aquifer bounds, but when reviewed by the user, these are false positives and are instead features such as sastrugi or gently undulating terrain. This research will help us better understand firn-aquifer drainage and its role in bringing water to glacier beds. This knowledge is necessary for understanding glacier flow in Southeast Greenland and thus ice sheet contribution to future sea level rise.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMC028.0006C
- Keywords:
-
- 0726 Ice sheets;
- CRYOSPHERE;
- 0750 Sea ice;
- CRYOSPHERE;
- 0758 Remote sensing;
- CRYOSPHERE;
- 0762 Mass balance;
- CRYOSPHERE