Investigating the influence of increased meltwater runoff on basal sliding in Northeast Greenland.

One of the consequences of rising temperatures observed in Northeast Greenland during the last decades is the increase in surface melting. Meltwater runoff can reach the bed and influence the ice flow regime through changes in basal conditions. Yet, depending on the drainage system, meltwater increase can have opposite effects on basal sliding and there is no consensus yet on the mechanisms that govern this hydrological switch. Here we present some advances in understanding the effects of surface meltwater percolation on ice dynamics at the Northeast Greenland Ice Stream (NEGIS) by investigating surface melt-basal sliding interactions at various temporal scales. To this end, we make use of a fully coupled model approach, comprising the finite-element ice-flow model Elmer/Ice and the hydrological scheme GlaDS. The latter is capable of representing the water drainage at all levels of the ice column. High resolution daily surface mass balance reconstructions available for the years 2014-2018 and simulated by the surface energy balance model COSIPY are used to force the ice-flow model. After first sensitivity tests aiming to explore the parameters of the ice-flow-hydrology system model, a fully coupled simulation for the period 2014-2018 is performed. This advanced modelling framework allows us to tackle the response of the NEGIS ice flow to seasonal and multi-annual variations in surface melt through changes in the drainage system.