East Antarctica’s Totten Glacier has been revealed to be more unstable than previously anticipated. New research has found that portions of the glacier that were thought to be on stable ground are actually floating on seawater, prompting concerns over the ice sheet’s stability, and its potential to significantly contribute to the acceleration of sea level rise.

Totten Glacier is a flowing ice field that is more than three-quarters the size of Texas, and holds a massive volume of ice that could raise sea levels by 3.5 meters (11.5 feet) if it were to completely melt.

Additionally, it is one of Antarctica’s fastest-flowing glaciers, and has been the subject of numerous studies and surveys in recent years, research projects that paint an increasingly unstable picture of the ice field. This new survey, employing seismic sensors to map the extent and depth of the ice, has found that the ocean extends much farther inland under the ice than previously thought — by hundreds of kilometers at that.

"In some locations we thought were grounded, we detected the ocean below indicating that the glacier is in fact floating," explains Central Washington University’s Paul Winberry, part of the on-site survey team.

This new discovery regarding the ice sheet’s footing, or relative lack thereof, means that the Totten Glacier is being warmed by not only the air above the sheet, but also from the warming seawater seeping below it. This was previously only a concern under the glacier’s ice shelf, where the ice flow extends out into the ocean, but the extent of the ocean’s reach inland vastly increases Totten’s vulnerability.

"It also means the Totten might be more sensitive to climate variations in the future," Winberry adds, indicating that as the climate warms, the precariousness of Totten’s situation increases. NASA estimates that Antarctica has already lost 125 billion tonnes of ice between 2002 and 2016, raising sea levels by more than a third of a millimeter per year, or roughly 1/5th of an inch over that 14-year period.