The processes controlling advance and retreat of outlet glaciers in fjords draining the Greenland Ice Sheet remain poorly known, undermining assessments of their dynamics and associated sea-level rise in a warming climate. Mass loss of the Greenland Ice Sheet has increased six-fold over the last four decades, with discharge and melt from outlet glaciers comprising key components of this loss. Here we acquired oceanographic data and multibeam bathymetry in the previously uncharted Sherard Osborn Fjord in northwest Greenland where Ryder Glacier drains into the Arctic Ocean. Our data show that warmer subsurface water of Atlantic origin enters the fjord, but Ryder Glacier’s floating tongue at its present location is partly protected from the inflow by a bathymetric sill located in the innermost fjord. This reduces under-ice melting of the glacier, providing insight into Ryder Glacier’s dynamics and its vulnerability to inflow of Atlantic warmer water.

No abstract

The Greenland ice sheet has had an increasingly negative mass balance during recent decades (Mouginot et al., 2019), and has been responsible for ∼0.76 ± 0.1 mm/yr of global sea level rise (SLR) between 2005(Cazenave et al., 2018. Greenland was the most important cryospheric contributor to SLR during this period, above Mountain glaciers (0.74 ± 0.1 mm/yr) and Antarctica (0.42 ± 0.1 mm/yr) (Cazenave et al., 2018). Mass losses in Greenland are driven by climatic and oceanographic warming (Christoffersen et al.