Ryder Glacier in northwest Greenland is shielded from warm Atlantic water by a bathymetric sill

TLDR

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. We acquired oceanographic data and multibeam bathymetry in Sherard Osborn Fjord, northwest Greenland, where Ryder Glacier drains into the Arctic Ocean. Mass loss of the Greenland Ice Sheet has increased six‑fold over the last four decades, largely from outlet glacier discharge and melt, and our data show that warmer Atlantic subsurface water enters Sherard Osborn Fjord but is partly blocked by a bathymetric sill protecting Ryder Glacier’s floating tongue, thereby reducing under‑ice melting and informing its dynamics and vulnerability to warmer inflow.

Abstract

Abstract 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.