Subproject 2: Basal Melting at the 79 North Glacier and Ocean Circulation

Observations in international programs with leading participation of AWI show a significant warming of the Atlantic Water flow into the subpolar North Atlantic and the Arctic Ocean. Based on these results the question is raised whether and how strongly an oceanic warming effects and may destabilize the marine terminating glaciers on the northeast coast of Greenland in the future. The glaciers located in Northeast Greenland - the largest of which being the 79 North Glacier (hereafter referred as 79NG) - were considered to be among the most stable in the past few years compared to those along the western and southern coast of Greenland. In this sub-project, the impact of warm Atlantic waters on basal melting under the ice tongue of the 79NG will be investigated. Basal melting below the glacier tongue is assumed to be a major factor in the destabilization of the glacier and the ice stream feeding into it. However, the conduction of the measurements required represents a special technological and logistical challenge.

For the acquisition of basal melting, phase-sensitive radar stations were installed on the floating part of the 79NG during the iGRIFF campaign 2017. These stations measure the ice thickness continuously over the course of the year. For a better spatial distribution of mean annual melt rates, these time series have been supplemented by comprehensive radar measurements and were completed by repeated measurements in 2018. In summers 2016 and 2017, we measured water mass characteristics, current velocities, as well as the seafloor topography aboard the research icebreaker Polarstern. In addition, moorings were deployed right in front of the glacier tongue aiming at measuring current speeds, temperatures, and salinities continuously throughout an entire year covering the whole water column. Based on these measurements we will study the strength and variability of the oceanic heat transport toward the glacier aiming a better understanding of the role of the ocean in melting the glacier from below.

Subproject 2 will also coordinate the synthesis of the regional freshwater budget in Northeast Greenland within this joint BMBF project.