Using ICESat-2 and Operation IceBridge Altimetry for Supraglacial Lake Depth Retrievals
Abstract
Supraglacial lakes and melt ponds occur frequently in the ablation zones of Antarctica and Greenland. The presence of water on the ice surface produces a positive albedo feedback, wherein meltwater ponding enhances shortwave absorption that in turn leads to enhanced melt. Furthermore, lake and ponds are important drivers of hydrofracture, which may lead to bed lubrication or enhanced ice shelf breakup. Therefore, detection of supraglacial meltwater is important for understanding the evolution of the glacier surface energy balance and glacier dynamics.
In this study, we use data from the Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) over the Amery Ice Shelf and the Airborne Topographic Mapper (ATM) collected over Hiawatha Glacier in Greenland, to develop supraglacial lake depth retrieval algorithms that we hope to eventually apply to automatically mapping supraglacial lake depths globally. To detect lakes and ponds, we examined range binned histograms of the ATL03 (ICESat-2 geolocated photons) and ILATM1B (ATM Elevation and Return Strength) data products. Water surfaces produce highly concentrated photons that allow the algorithm to define the extent of the track that intersects the lake surface with relatively high confidence. Lake beds were then defined as concentrated photon returns occurring below the identified lake surface. A refraction correction and, for ICESat-2, a refinement to the bottom-finding algorithm were applied before estimating lake depth. With the data currently available, we successfully retrieved the depths of 12 supraglacial lakes with the ATM lidar and 4 lakes with ICESat-2. Lake/pond depths generally ranged between 2-5 m, with the deepest lakes appearing on Hiawatha Glacier. The laser signal was frequently lost for lakes deeper than 8 m, making precise measurements difficult. As ICESat-2 collects more data, we expect to continue this work to retrieve meltwater estimates over ice sheets. Both ICESat-2 and ATM obtained measurements from Greenland during its early and intense melting onset in May and June, allowing for further retrievals as the data are released. Further work will compare altimeter retrievals with optical depth estimates from Landsat-8 and Sentinel-2.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C31C1556F
- Keywords:
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- 3360 Remote sensing;
- ATMOSPHERIC PROCESSES;
- 0726 Ice sheets;
- CRYOSPHERE;
- 0750 Sea ice;
- CRYOSPHERE;
- 4556 Sea level: variations and mean;
- OCEANOGRAPHY: PHYSICAL