Pathways of meltwater export from Petermann Glacier, Greenland

Intrusions of Atlantic Water cause basal melting of Greenlands marine terminating glaciers and ice shelves such as that of Petermann Glacier, in northwest Greenland. The fate of the resulting glacial meltwater is largely unknown. It is investigated here, using hydrographic observations collected during a research cruise in Petermann Fjord and adjacent Nares Strait on board I/B Oden in August 2015. A three end-member mixing method provides the concentration of Petermann ice shelf meltwater. Meltwater from Petermann is found in all of the casts in adjacent Nares Strait, with highest concentration along the Greenland coast in the direction of Kelvin wave phase propagation. The meltwater from Petermann mostly flows out on the northeast side of the fjord as a baroclinic boundary current, with the depth of maximum meltwater concentrations approximately 150 m and shoaling along its pathway. At the outer sill, which separates the fjord from the ambient ocean, approximately 0.3 mSv of basal meltwater leaves the fjord at depths between 100 and 300 m. The total geostrophic heat and freshwater fluxes close to the glacier’s terminus in August 2015 were similar to those estimated in August 2009, before the two major calving events that reduced the length of Petermann’s ice tongue by nearly a third, and despite warmer inflowing Atlantic Water. These results provide a baseline, but also highlight what is needed to assess properly the impact on ocean circulation and sea level of Greenland’s mass loss as the Atlantic Water warms up