Marine Ice Sheet Instability Triggered Rapid Retreat of Major West Antarctic Glacier

Nature Climate Change, 4 December 2023

The massive Pine Island Glacier in West Antarctica underwent a fifty-year period of “marine ice sheet instability” (MISI), a rapid cycle of retreat and ice loss that ended only when it reached a new stable position on bedrock in the 1990s. This glacier began rapidly retreating in the 1940s, when warm ocean water entered a cavity beneath the ice shelf. Previously balanced on a stable ridge, the ice slipped down an inward-sloping section of bedrock and retreated nearly 40 kilometers inland, with the most extreme loss in the final two decades. Between the 1970s-1990s, Pine Island was responsible for one-third of ice loss from West Antarctica, and one-eighth from Antarctica as a whole. Over subsequent cooler decades, Pine Island was unable to recover and could not return to its original position from the 1940s. Although Pine Island is no longer in a period of MISI, it remains one of the fastest-retreating glaciers in Antarctica, and has contributed more to global mean sea-level rise in recent decades than any other. Researchers warn that other glaciers in the Amundsen Sea region could have similar instability thresholds, which if crossed due to continued warming from fossil fuel emissions could lead to massive ice loss over coming decades and centuries as these huge West Antarctic glaciers enter unstable phases of retreat.

https://www.nature.com/articles/s41558-023-01887-y