Modelling the evolution of the weathering crust

The weathering crust is a porous layer of ice found at an ice sheet surface, formed by shortwave radiation penetrating below the surface and causing internal melting. It is a dynamic hydrological system that acts to transport meltwater, impurities, and microbes across the ice sheet surface into larger-scale hydrological features such as surface streams. The weathering crust is very variable, growing and decaying on the order of hours and days in response to changing weather conditions, with consequences for the surface albedo as well as meltwater storage and transport. The albedo is impacted both by the weathering crust structure and the presence of microbes and impurities (for example in the south-western Greenland ‘dark zone’). We have developed two mathematical models to investigate the evolution of the weathering crust and microbes over space and time: a one-dimensional model for the vertical structure, and a depth-integrated model to explore the lateral extent of the weathering crust and transport of meltwater. We present solutions generated by idealised forcings as well as observations from the field. This explains the observed response of the weathering crust to short-term changes in weather, and provides insight into the longer-term response of the weathering crust and algal blooms to climate change.