Antarctica's 'Doomsday Glacier' May Raise Sea Levels Twice as Much as Previously Estimated, Study Warns

Antarctica's Thwaites Glacier, often referred to as the 'Doomsday Glacier,' poses a greater threat than previously understood, according to a new study published in Nature Communications. Researchers have found that warming ocean waters are eroding the glacier's base faster than anticipated, potentially doubling previous estimates for its contribution to global sea level rise by the year 2100.

The Thwaites Glacier, located in western Antarctica and covering an area larger than Great Britain, could cause sea levels to rise by 26 inches (65 centimeters) if it were to collapse entirely. While a complete collapse is not considered imminent, the glacier is accelerating towards a more precarious state. The new study suggests this acceleration could lead to an additional 1.2 inches (30 millimeters) of sea level rise by 2100.

This revised projection stems from a new model that incorporates a more accurate understanding of the processes occurring beneath the glacier's base. "Most projections to date have struggled to match the rapidity of the mass loss because of missing physics; our new model with more complete physics can match the record and then produces projections that are twice as large as before," said co-author Professor Eric Rignot from the University of California. He added that these findings indicate a "greater risk of and exposure to coastal flooding than anticipated in the coming decades."

Previous models struggled to reconcile predictions with satellite data showing an alarmingly fast rate of thinning and retreat for Thwaites. The models predicted a slower movement into the ocean than observed. The new research addresses this by acknowledging that glaciers like Thwaites end not at a stable "grounding line" where ice leaves land and begins floating, but in a "grounding zone"—a broad area where warm ocean water seeps deep underneath the ice sheet.

Utilizing data from the Finnish ICEYE satellite constellation, which measures small ice surface movements, researchers found that seawater penetrates several miles beneath the grounded ice. This intrusion lifts the ice during tidal cycles, flushing the grounding zone with warm, pressurized seawater that is being pushed towards the Antarctic coastline by climate-change-altered currents.

The new model, reconstructed from 1990s data to the present, shows historical glacier change that is four times more pronounced than traditional models. A significant concern is that these grounding zone processes are accelerating the detachment of the Thwaites Glacier from stabilizing seabed ridges, such as the Mouginot Ridge. This detachment could trigger more rapid collapse.

According to the study, there is now a 60% probability that Thwaites will become disconnected from the Mouginot Ridge by the end of the century. "Once that ridge is unpinned, the glacier will continually retreat across a predominantly retrograde seafloor toward its next topographic high, the South Ridge," explained lead author Dr. Mattia Poinelli of UC Irvine.

This development comes amid other concerns about the Thwaites Eastern Ice Shelf, a massive ice structure that holds back the flow of ice into the sea. This shelf, over 1,150 feet thick and covering 580 square miles, is being thinned at an alarming rate by warming Antarctic oceans. In May, Dr. Robert Larter, a marine geophysicist at the British Antarctic Survey, warned that the shelf's breakup is "very likely to happen sometime this year."

The Thwaites Glacier is a critical factor in projecting global sea level rise. Its instability is linked to the West Antarctic Ice Sheet, which lies deeply below sea level, making it a gateway for a substantial portion of Antarctica's potential sea level contribution. The collapse of the Thwaites Glacier alone could lead to a global sea level increase of one to two meters (three to six feet), with the potential for more than twice that from the entire West Antarctic Ice Sheet.