Sea-level rise projections of Petermann Glacier, Greenland, modeled using synchronously coupled subglacial hydrology and ice flow dynamics

Greenland ice shelves are known to display seasonal speedups of ice velocity which can be attributed to ice front position or to meltwater runoff, depending on which glacier is being examined. However, it remains uncertain if the seasonality of glacier speed will be impacted by climate change in the coming century. Current projections of glacier dynamics under 21st century climate forcings do not include subglacial hydrology, so it also remains unknown if it will play any important role in evolving glacier dynamics under different climate change scenarios, or ultimately have an impact on sea-level rise projections. Here we present a model with synchronous coupling of ice dynamics and subglacial hydrology applied to Petermann Glacier in northern Greenland. Petermann exhibits a summer-time acceleration of roughly 15% as compared to its baseline winter velocity, which is likely the result of subglacial hydrology. Although it has been relatively stable in recent years, as one of the largest marine terminating glaciers in northern Greenland, whether or not Petermann remains stable will have a significant impact on the sea-level contribution of the northern sector of the ice-sheet. We use climate through 2100 to investigate how the subglacial hydrologic system may evolve in a warmer climate and to test if including hydrology changes the stability of Petermann under future climate scenarios using the Ice-sheet and Sea-level System Model (ISSM) which includes the Glacier Drainage System (GlaDS) model. We compare glacier evolution and projected sea-level rise for three model configurations: one with synchronously coupled subglacial hydrology and ice dynamics, a second with asynchronous coupling where subglacial hydrology is calculated with static ice geometry and velocity but ice dynamics are calculated using effective pressure from GlaDS output, and a third where subglacial hydrology is excluded entirely from the model setup.  Results show a significant increase in projected sea-level rise by the end of the century and differing patterns of grounding line migration and ice thinning when subglacial hydrology is included in the model configuration for Petermann.