Nature Geoscience, 13 January 2022
Scientists are observing unusually rapid retreat along the undersides of several glaciers in the Amundsen Sea of West Antarctica. Rising global temperatures send fast-moving currents of relatively warm seawater into cavities along the base of these glaciers and their adjoining ice shelves. These currents have accelerated the melting of ice along the grounding line (where the ice detaches from the bedrock and becomes afloat), eating away at the glacier from the bottom. Once the glacier loses contact with the bedrock, it becomes more unstable, and subject to melting and potentially rapid collapse. In 2017, the grounding line of Pope Glacier retreated nearly 12 kilometers inland, an almost unprecedented measurement for a single year; and the Smith and Kohler glaciers retreated around 2.4 and 1.3 kilometers, respectively. The Pope, Smith, and Kohler glaciers are relatively small by Antarctic standards, but the physical processes driving their retreat also operate on the massive neighboring Thwaites and Pine Island glaciers. These two glaciers alone hold 1.2 meters of potential sea-level rise and, if they collapse, may destabilize the rest of West Antarctica, which holds an additional 3-4 meters. Close monitoring of these processes is critical to estimating how quickly sea levels may rise as a result of melting on Antarctica. However, it appears increasingly clear that current global warming already is driving changes; adding to the urgency of emissions reductions to slow warming, and resulting current and future flooding of global coastlines.