Subproject 4: Basal meltwater distribution around Greenland

Basal melting is one of the major causes of the Greenland Ice Sheet mass loss and global sea level rise. The accelerated melting observed in recent decades is mainly caused by the inflow of warmer water into the fjords. However, knowledge about basal melt rates is limited, and open questions exist regarding the processes that control the interaction of the oceans with marine terminating glaciers. In addition, it is unclear how much meltwater from the fjords reaches the boundary current, and which processes govern this. Also, the fraction of meltwater that is exported from the marginal stream into the interior of the European North Sea and the subpolar North Atlantic is unknown, as is the spatial and temporal variability of these processes. Uncertainties in basal melt rates and in the distribution of meltwater in climate models can lead to uncertainties in ocean circulation, and thus uncertainties in heat and freshwater flows into and out of the subpolar North Atlantic, the Norwegian Arctic, and the Arctic. In the GROCE subproject TP4, a method is to be applied which has already successfully determined the distributions of the basal melt water distribution and its changes in the Southern Ocean: the measurement and interpretation of the distributions of helium and neon isotopes from the glacier tongue over the fjords, the boundary currents and the interior basin. Due to the almost 1000 times higher concentrations in pure basal melt water, meltwater levels up to 0.035 percent can be determined in the ocean. The pathway from the glacier tongue to the boundary current is investigated at the 79 ° N glacier, as is the distribution of melt water between the boundary current and the western Norwegian Sea.