Extended Data Fig. 7: Gridded velocity and thickness data.

This work required knowledge of ice velocity and thickness beyond the current measurable extents of the ice sheet. We combine data from several sources (Methods) to generate complete gridded velocity and thickness fields that cover the entire domain of interest. Ice velocity and thickness values are unrealistic in the open ocean but are reasonable and well constrained within fjords and close to the current extents of the ice sheet, for which the values are used in this work. a–d, The entire GrIS. e–h, Detailed views of the region surrounding the terminus of Jakobshavn Isbræ. Maps created with Arctic Mapping Tools for MATLAB⁵⁴ using geographic outlines developed in this work.