The Baffin Bay Ice Shelf stabilized three adjacent ice sheets during the last glacial period

Global ice volume peaked between ~26,500 and 19,000 years ago and resulted in the Laurentide, Innuitian and Greenland ice sheets coalescing in Baffin Bay, a semi-enclosed basin between Greenland and Canada. However, the configuration of their marine terminating margins, which help establish the boundary conditions and sensitivity to processes that govern ice-sheet retreat, remains unclear. Here we compile bathymetric data and report a geomorphic study of the Baffin Bay continental slope. We provide evidence for slope-grounded ice during the last glacial interval and trace its maximum depth imprint around most of Baffin Bay. We interpret ice-contact features to have resulted from a basin-spanning ice shelf that was ~1,400–2,100 m thick, once corrected for relative sea level. The extensive ice shelf (150,000 km2), supported by the basin geometry, buttressed, mechanically coupled, and promoted thickening of the adjacent ice sheets. Informed by sediment cores, we infer that ice-shelf collapse triggered rapid ice-sheet retreat, linking abrupt Northern Hemisphere ice-sheet instability to embayment-scale ice-shelf dynamics. The Baffin Bay Ice Shelf shows that ice-shelf loss can rapidly reorganize marine ice sheets, an analogue for how weakening buttresses may accelerate future Antarctica ice-stream retreat. An enormous ice shelf spanned Baffin Bay during the last glacial period, and its rapid retreat during the last deglaciation probably destabilized the surrounding ice sheets, according to an analysis of bathymetric data