Simulating the formation and decay of supraglacial lakes in South-West Greenland

The dynamics of the Greenland Ice Sheet (GrIS) is greatly affected by surface meltwater that is routed from the surface to the bed, for example when a supraglacial lake (SGL) drains. The South-West Greenland Ice Sheet (SWGrIS) has an abundance of such lakes that form and decay over every hydrological year. In case a crevasse is opened up underneath an SGL, the lake water is likely to drain via the crevasse into the ice-sheet’s bed. This in turn influences the ice sheet motion by increasing the lubrication at the ice-sheet’s base. SGLs may also either drain laterally via a supra-glacial meltwater channel or the water they contain can stay put throughout the hydrological year, refreezing in the winter. These processes may affect the ice rheology in addition to influencing ice flow. While simulating the future evolution of the GrIS, it is thus important to account for processes associated with the evolution of SGLs. Until now, however, none of the existing ice sheet models have fully accounted for these processes, in part because no hydrological model yet includes them all. Here we propose a new process-based hydrological model for the SWGrIS which fully accounts for the evolution of  SGLs. The model consists of four units. The first is a surface water routing unit where the daily-generated surface meltwater is routed assuming steepest decent into the surface depressions forming SGLs. The second unit uses principles of Linear Elastic Fracture Mechanics (LEFM) to deal with the scenario where an SGL drains into the bed through an underlying crevasse. The third deals with the SGL drainage event that occurs when a surface meltwater channel gets incised though the ice sheet’s surface due to erosion from the SGL’s overflowing meltwater i.e. channel incision. Finally, the fourth unit simulates the freezing/unfreezing of SGLs by calculating the energy balance at the SGL’s surface. Using this model forced by Modèle Atmosphérique Régionale (MAR) derived daily surface melt-water values we quantify a) the amount and location of surface meltwater injection to the ice-sheet’s bed via moulins or crevasses and ,b) the meltwater that is either  retained in SGL or drained overland via meltwater channels and stored elsewhere over the period 2011-2020, in the Leverett glacier catchment. In the future, we plan to integrate this hydrological model with the sophisticated state-of-the-art BISICLES ice sheet model.