A Decade of Ocean Changes Impacting the Ice Shelf of Petermann Gletscher, Greenland

Hydrographic data collected during five summer surveys between 2002 and 2015 reveal that the subsurface ocean near Petermann Gletscher, Greenland, warmed by 0.015 degrees +/- 0.013 degrees C yr(-1). New 2015-16 mooring data from beneath Petermann Gletscher's ice shelf imply a continued warming of 0.025 degrees +/- 0.013 degrees C yr(-1) with a modest seasonal signal. In 2015, we measured ocean temperatures of 0.28 degrees C near the grounding line of Petermann Gletscher's ice shelf, which drove submarine melting along the base of the glacier. The resultant meltwater contributed to ocean stratification, which forced a stronger geostrophic circulation at the ice shelf terminus compared with previous years. This increased both the freshwater flux away from the sub-ice shelf cavity and the heat flux into it. Net summertime geostrophic heat flux estimates into the sub-ice shelf cavity exceed the requirement for steady-state melting of Petermann Gletscher's ice shelf. Likewise, freshwater fluxes away from the glacier exceed the expected steady-state meltwater discharge. These results suggest that the warmer, more active ocean surrounding Petermann Gletscher forces non steady state melting of its ice shelf. When sustained, such melting thins the ice shelf.