Freshwater flux and spatiotemporal simulated runoffvariability into Ilulissat Icefjord, West Greenland, linked to salinity and temperature observations near tidewater glacier margins obtained using instrumented ringed seals

The distribution of terrestrial surface runoffto Ilulissat Icefjord, west Greenland, is simulated for the period 2009-13 to better emphasize the spatiotemporal variability in freshwater flux and the link between runoffspikes and observed hydrographic conditions at the Greenland Ice Sheet tidewater glacier margins. Runoffmodel simulations were forced with automatic weather station data and verified against snow water equivalent depth, equilibrium line altitude, and quasi-continuous salinity and temperature observations obtained by ringed seals. Instrumented seals provide a novel platform to examine the otherwise inaccessible waters beneath the dense ice mélange within the first 0-10 km of the calving front. The estimated mean freshwater flux from land was 70.6 ± 4.2 km³ yr^-1, with an 85% contribution of ice discharge from Jakobshavn Isbrae (also known as Sermeq Kujalleq), 14% from runoff, and the remaining 1% from precipitation on the fjord surface area, subglacial geothermal melting, and frictional melting due to basal ice motion. Runoffwas simulated to be present from May to November and to vary spatially according to glacier cover and individual catchment size. Salinity and temperature observations correlate (significantly) with simulated runofffor the upper part of both the main fjord and southern fjord arm. Also, at the tidewater glacier margins in the northern and southern arm of Ilulissat Icefjord, salinity changes in the upper water column (upper 50 m) are significant after temporal spikes in runoffduring late summer, while small-amplitude runoffvariability during the recession of runoffdid not create a clear signal in observed salinity variability. Also, in the southern arm near the glacier margin (between 100-and 150-m depth), the heterogeneous distribution in salinity could be because of the mixing of meltwater going upward from passing the grounding line. The effect of runoffspikes on observed salinity is less pronounced near the ice margin of Jakobshavn Isbrae than in the north and south arms.