Recent irreversible retreat phase of Pine Island Glacier

Pine Island Glacier (PIG), a part of the West Antarctic marine ice sheet, has recently undergone substantial changes including speed up, retreat and thinning. Theoretical arguments and modelling work suggest that marine ice sheets can become unstable and undergo irreversible retreat. Here, we use an ice-flow model validated by observational data to show that a rapid PIG retreat in the 1970s from a subglacial ridge to an upstream ice plain was self-enhancing and irreversible. The results suggest that by the early 1970s, the retreat of PIG had reached a point beyond which its original position at the ridge could not be recovered, even during subsequent periods of cooler ocean conditions. The irreversible phase ended by the early 1990s after almost 40 km of retreat and 0.34 mm added to global mean sea level, making PIG the main contributor from the Antarctic ice sheet in this period.