Fig. 1: Locations of Sherard Osborn and Petermann fjords where, respectively, Ryder Glacier and Petermann Glacier drain the North sector of the GrIS.
From: Ryder Glacier in northwest Greenland is shielded from warm Atlantic water by a bathymetric sill
a Ice velocity, in m per year, of the marine outlet glaciers from the MEaSUREs project44. b Newly collected multibeam bathymetry of the Sherard Osborn Fjord reveals the inner and outer bathymetric sills separated by a basin with a maximum water depth of 890 m. The deepest passages over the sills are marked along with their depths. c Multibeam bathymetry collected in Petermann Fjord in 201517 shows a pronounced sill located at the mouth of the fjord. The deepest threshold of this sill is 443 m and the maximum depth of Petermann Fjord is 1158 m. The white dots in a and b are the conductivity, temperature and depth (CTD) stations shown in Fig. 3. The white dots with a red border are averaged and used in the plume modelling. Stations connected with a white line and marked with station numbers are used to construct the water temperature profiles X–X’ and Y–Y’ in Fig. 3. Three additional profiles, S1–S1’, S2–S2’ and S3–S3’, along the paths of the black (along fjord) and grey (across fjord) lines are shown in the Supplementary Fig. 2. Station 44 in Petermann Fjord is marked with its number because it is shown in Fig. 5. The background image is from Radarsat where ice and land show up in different shades of grey while open water is black. The 1917 ice-tongue extents are digitized from historical maps by Danish geologist Lauge Koch23, while 2010 and 2019 are inferred from satellite images.
