Towards understanding supraglacial river networks in southwest Greenland

Authors: Rohi Muthyala*, Rutgers University, Asa Rennermalm, Rutgers University, Sasha Leidman, Rutgers University, Matthew G Cooper, University of California-Los Angeles, Sarah Cooley, Brown University, Lawrence C Smith, University of California-Los Angeles, Dirk van As, Geological Survey of Denmark and Greenland
Topics: Cryosphere, Water Resources and Hydrology, Climatology and Meteorology
Keywords: Greenland, ice sheet, meltwater, supraglacial streams, discharge, energy balance model
Session Type: Paper
Day: 4/6/2019
Start / End Time: 9:55 AM / 11:35 AM
Room: Truman, Marriott, Mezzanine Level
Presentation File: No File Uploaded

Meltwater produced at the surface of Greenland ice sheet is one of the main contributors for sea-level rise and this meltwater is efficiently transported across the surface through supraglacial river networks. However, due to the lack of in situ observations, little is known about the seasonal variation or current models’ ability to simulate discharge from these river networks. In this study, we report and compare two months (22 June – 14 August 2016) of discharge observations with modeled discharge for a ~0.7 km2 supraglacial catchment in the ablation zone of southwest Greenland. Modeled discharge is calculated by a point surface energy balance model forced with meteorological and radiation data from a nearby PROMICE/GAP KAN_L, automated weather station. Model discharge co-varies strongly with in situ discharge, but overestimates the total discharge flow. This model bias is primarily seen over the first half of the melt season and is diminished over the second half of the season, due to the model assumption of neglecting meltwater routing throughout the catchment. The dominant driver of the ice sheet discharge throughout the season is net shortwave radiation. However, during the peak flow events, especially when the shortwave radiation dropped considerably because of overcast conditions, net longwave radiation and turbulent heat fluxes are significant drivers of surface melting and thus meltwater discharge. Therefore, long term supraglacial stream observations such as these are useful in understanding the predominant drivers of surface melt throughout the season.

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