Reconstruction of the Greenland Ice Sheet surface mass balance and the spatiotemporal distribution of freshwater runoff from Greenland to surrounding seas

Abstract. Knowledge about variations in runoff from Greenland to adjacent fjords and seas is important for the hydrochemistry and ocean research communities to understand the link between terrestrial and marine Arctic environments. Here, we simulate the Greenland Ice Sheet (GrIS) surface mass balance (SMB), including refreezing and retention, and runoff together with catchment-scale runoff from the entire Greenland landmass (n = 3,272 simulated catchments) throughout the 35-year period 1979–2014. SnowModel/HydroFlow was applied at 3-h intervals to resolve the diurnal cycle and at 5-km horizontal grid increments using ERA-Interim (ERA-I) reanalysis atmospheric forcing. Simulated SMB was low compared to earlier studies, whereas the GrIS surface conditions and precipitation were similar. Variations in meteorological and surface ice and snow cover conditions influenced the seasonal variability in simulated catchment runoff; variations in the GrIS internal drainage system were assumed negligible and a time-invariant digital elevation model was applied. Approximately 80 % of all catchments showed increasing runoff trends over the 35 years, with on average relatively high and low catchment-scale runoff from the SW and N parts of Greenland, respectively. Outputs from an Empirical Orthogonal Function (EOF) analysis were combined with cross-correlations indicating a direct link (zero lag time) between modeled catchment-scale runoff and variations in the large-scale atmospheric circulation indices North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO). This suggests that natural variabilities in AMO and NAO constitute major controls on catchment-scale runoff variations in Greenland.