Rapid, buoyancy-driven ice-sheet retreat of hundreds of metres per day
Christine L. Batchelor, Frazer D. W. Christie, Dag Ottesen, Aleksandr Montelli, Jeffrey Evans, E. K. Dowdeswell, Lilja Rún Bjarnadóttir, Julian A. Dowdeswell
Abstract
Rates of ice-sheet grounding-line retreat can be quantified from the spacing of corrugation ridges on deglaciated regions of the seafloor1,2, providing a long-term context for the approximately 50-year satellite record of ice-sheet change3–5. However, the few existing examples of these landforms are restricted to small areas of the seafloor, limiting our understanding of future rates of grounding-line retreat and, hence, sea-level rise. Here we use bathymetric data to map more than 7,600 corrugation ridges across 30,000 km2 of the mid-Norwegian shelf. The spacing of the ridges shows that pulses of rapid grounding-line retreat, at rates ranging from 55 to 610 m day−1, occurred across low-gradient (±1°) ice-sheet beds during the last deglaciation. These values far exceed all previously reported rates of grounding-line retreat across the satellite3,4,6,7 and marine-geological1,2 records. The highest retreat rates were measured across the flattest areas of the former bed, suggesting that near-instantaneous ice-sheet ungrounding and retreat can occur where the grounding line approaches full buoyancy. Hydrostatic principles show that pulses of similarly rapid grounding-line retreat could occur across low-gradient Antarctic ice-sheet beds even under present-day climatic forcing. Ultimately, our results highlight the often-overlooked vulnerability of flat-bedded areas of ice sheets to pulses of extremely rapid, buoyancy-driven retreat. Analysis of more than 7,600 corrugation ridges on the Norwegian continental shelf shows that rapid grounding-line retreat of several hundred metres per day occurred across low-gradient ice-sheet beds during the last deglaciation.