Seasonal and inter annual effects of meltwater runoff on ice dynamics in Northeast Greenland

The large amount of meltwater reaching the base of a glacier at the beginning of the melt season accelerates its ice flow, as meltwater pressurised in cavities acts as bed lubricant. Proceeding in the melt season, if the erosive power of basal water becomes high enough to prevail on the creep-induced closure of such cavities, channels may form. In this regime, water is efficiently drained towards the ice front, basal pressure abates and ice flow decelerates. The temporary speed-up and deceleration throughout the melt season has been observed in many glaciers in Greenland, especially in the southwest. There, more observations are available and the ablation zone extends hundreds of km inland. Yet, there is no evidence that Northeast Greenland follows this hydrology-induced dynamic behaviour. In fact, very few observations of flow variability during the melt season are available for this area, hampering our understanding of impacts of meltwater on the ice dynamics in these remote arctic regions. In this work we run a fully coupled ice-flow-hydrology model (Elmer/Ice coupled to GlaDS) to explore the feedbacks between surface meltwater and ice-flow variations over the whole basin of Northeast Greenland. We address both seasonal and annual timescales by running the coupled model for successive melt seasons (from May 2016 to the end of September 2018). To do so, we make use of daily surface mass balance and runoff data computed by a fully-fledged surface energy balance model (COSIPY) resolving snowpack processes. Our simulations show a seasonal speed-up due to increase in melt water pressure at the base, followed by a decrease in velocities due to the activation of a channelised system beneath the ice sheet. Our results suggest that the Northeast Greenland presents a complex hydrological system that is comparable to other regions of the ice sheet and hint at hydrology-dynamics mechanisms to be a potential controlling factor in the evolution of the area.