Abstract
Helheim Glacier, located in southeast Greenland, is a large outlet glacier that drains approximately 8% of the Greenland Ice Sheet (GIS), emptying into Sermilik Fjord. The glacier speed and terminus location have both shown large variability over the past decade, with significant impacts on the freshwater and heat transport within the fjord, as well as on the mass balance of the GIS. Yet the cause for these changes is still debated. Here we present full year time series of velocity and hydrographic observations collected in Sermilik Fjord and the adjacent continental shelf over 2009-2010. The velocity data show that tidal circulation is small inside Sermilik Fjord, but that significant variability exists over a wide range of frequencies that correspond to a complex set of ocean dynamics. We discuss the impact of this circulation on the heat transport to the glacier, which is ultimately responsible for submarine melting. Shelf waters provide the boundary conditions for the fjord circulation, so their dynamics and hydrography are also investigated using the newly collected data combined with historic datasets. Lessons learned in this system provide general guidance for several other large outlet glacier systems in Greenland and elsewhere.