COASTAL CHALLENGESModeling Thawing at Base of Antarctic Ice Sheet

Published 15 September 2022

Across Antarctica, some parts of the base of the ice sheet are frozen, while others are thawed. Scientists show that if some currently frozen areas were also to thaw, it could increase ice loss from glaciers that are not currently major sea-level contributors.

Recent efforts using computational modeling to understand how melting ice in Antarctica will impact the planet’s oceans have focused on ice-sheet geometry, fracture, and surface melting – processes that could potentially trigger or accelerate ice-sheet mass loss. Now, researchers have identified an additional process that could have a similarly significant effect on the ice sheet’s future: thawing of the bed, known as basal thaw, at the interface of the land and the miles-thick ice sheet above it.

The new study identifies areas that are not currently losing large amounts of mass but could be poised to match some of the largest contributors to sea-level rise – such as Thwaites Glacier – if they thawed. Antarctica is roughly the size of the United States, and the susceptible regions comprise an area greater than California. The research was published Sept. 14 in Nature Communications.

“You can’t necessarily assume that everywhere that’s currently frozen will stay frozen,” said senior study author Dustin Schroeder, an associate professor of geophysics at the Stanford Doerr School of Sustainability. “These regions may be under-appreciated potential contributors.”

Unusual Suspects
The simulations were built on recent theoretical work showing that basal thaw could occur over short time scales. Using numerical ice sheet models, the study co-authors tested hypotheses about whether the onset of such thaw could lead to significant ice loss within a 100-year period. They found that triggering thaw led to mass loss in regions of the ice sheet that are not usually associated with instability and sea-level contributions at that time scale.

“There really has been little to no continental-wide work that looks at the onset of thawing – that transition from frozen ice to ice at the melting point, where a little bit of water at the bed can cause the ice to slide,” said lead study author Eliza Dawson, a PhD student in geophysics. “We were interested in learning how big an effect thawing could have and what regions of the ice sheet were potentially most susceptible.”