“Every Tenth of a Degree” Pushes Antarctica Closer to Potential New Threshold

Nature Geoscience, 25 June 2024

Modelers have long theorized about processes that might account for the unusually rapid sea-level rise from ice sheets in Earth’s distant past, such as marine ice cliff instability (MICI). This new study finds that runaway intrusion of warm seawater under the Antarctic ice sheet may be just such a process, and it could speed future sea-level rise far beyond current estimates, with very small increases in water temperature leading to huge ice loss. Building on recent research, authors find that even slight ocean warming could create a massive network of melt channels under the ice that allow seawater to flow potentially long distances inland, eroding the ice from below. The study warns that this process could trigger rapid ice loss with ocean temperatures just a few tenths of a degree higher than today, which will occur in coming decades if emissions are not dramatically reduced. The most vulnerable glaciers to this threshold behavior include Larsen and Getz, as well as Pine Island, currently Antarctica’s largest contributor to sea-level rise. Today’s global sea-level rise projections do not yet include these findings, which means that even the latest IPCC report may severely underestimate the potential upper limit of sea-level rise in coming decades and centuries.

Full paper: https://www.nature.com/articles/s41561-024-01465-7
Plain-language briefing: https://www.theguardian.com/environment/article/2024/jun/25/newly-identified-tipping-point-for-ice-sheets-could-mean-greater-sea-level-rise