Undersea ‘Storm’ Melts Ice Shelf of Terminal Glacier

A submerged “storm” is eroding the ice shelf that shields Antarctica’s Thwaites “Terminal” glacier, prompting concerns that scientists may be underestimating future sea level increases.

These storm-like currents, referred to as “submesoscale” features, can extend up to 10 kilometers wide and begin to form when water with varying temperatures and densities collides in the open ocean. This process is akin to hurricanes that arise from gas mixtures in the atmosphere. Similar to hurricanes, these currents can surge toward the coast, with Antarctica predominantly consisting of ice shelves—floating extensions of glaciers that project tens of kilometers into the ocean.

“Their movements are so unpredictable that halting them is quite challenging,” states Mattia Poinelli from the University of California, Irvine. “The only course of action is for them to become trapped beneath the ice.”

Poinelli and colleagues’ modeling indicates that these submesoscale formations were responsible for one-fifth of the total ice melt in the Thwaites Mountains and nearby Pine Island over a nine-month timeframe. This research marks the first attempt to quantify the influence of these storms across the entire ice shelf.

Ice shelves play a crucial role in hindering the movement of glaciers into the sea and shielding them from wave erosion. The vulnerable Thwaites Glacier annually loses 50 billion tons of ice and could raise sea levels by 65 centimeters if it collapses.

In the Antarctic waters, hundreds of meters of cold, fresh water float above warmer, saltier, deeper water. When a storm becomes enveloped within a cavity beneath an ice shelf, its swirling motions push cold surface water away from the center of the vortex, pulling warmer, deeper water into the cavity and melting the ice shelf from below.

This triggers a feedback mechanism where the melting cold freshwater interacts with the warmer, saltier water, amplifying the rotation of the underwater storm and increasing melting.

In 2022, a deep-sea float that measured temperature, salinity, and pressure was “captured” by a large rotating eddy trapped beneath the ice tongue of Stancombe Wills at another location along the Antarctic coast. The data retrieved from the captured floats showed that Katherine Hancock from Florida State University and her team estimated that the swirl causes 0.11 meters of annual melting beneath its ice tongue.

“This highlights the importance of understanding rotating eddies beneath ice shelves,” says Hancock.

The smaller submesoscale storms from Poinelli’s research are likely causing similar effects, she adds, indicating that swirling water bodies of varying sizes are contributing to significant ice melting. “There’s a need for more precise quantification,” Hancock emphasizes.

As temperatures rise and additional fresh snowmelt escapes from Antarctica, these underwater storms may increase in intensity, possibly leading to greater sea level rise than currently anticipated.

Tiago Dot of Britain’s National Oceanography Centre stated that the “unexpected” findings necessitate further observations beneath the ice shelf.

“Considering the shifts in wind patterns and sea ice around Antarctica, how much are we genuinely overlooking by not monitoring these smaller scales?” he questions.