Rapid, buoyancy-driven ice-sheet retreat of hundreds of metres per day.

• Published in: Nature
• Main Authors: Batchelor, Christine L, Christie, Frazer D W, Ottesen, Dag, Montelli, Aleksandr, Evans, Jeffrey, Dowdeswell, Evelyn K, Bjarnadóttir, Lilja R, Dowdeswell, Julian A
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Publishing Group 2023
• Subjects: Antarc*; Antarctic; Ice Sheet
• Online Access: https://doi.org/10.1038/s41586-023-05876-1; https://pubmed.ncbi.nlm.nih.gov/37020019

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.