A recent study published in Nature Geosciences warns that underwater eddies are aggressively melting the ice shelves of the Pine Island and Thwaites glaciers, two of the most important in Antarctica.
The finding has “far-reaching implications” for the global sea level rise, according to its authors.
The “End of the World” glaciers
Antarctica can be imagined as a fist with a thumb extending towards South America. At the base of that “thumb” is the Pine Island glacier, while next to it is Thwaites, known as the “Doomsday Glacier” for the devastating impact its collapse would have on sea levels.
In recent decades, both icy giants have experienced accelerated melting driven by ocean warming, especially at the point where they rise from the seabed and float as ice shelves.
Underwater storms: eddies that melt ice
The study is the first to analyze how the ocean melts ice shelves on hourly and daily scales, rather than seasons or years.
Researchers focused on submesoscale storms, rapidly changing ocean eddies that can extend up to 10 kilometers. They form when warm and cold waters meet, generating turbulence similar to atmospheric storms.
“Think of them as small spins of water that spin very fast, like when you stir water in a cup,” explained Mattia Poinelli, a researcher at the University of California, Irvine, and a NASA collaborator.
These eddies move under the ice shelves, trapped between their rough base and the seabed. There, they stir warm water from deep layers, intensifying melting when it hits the vulnerable ice.
Measured impact: 20% of melting in nine months
Using computational models and real data from ocean instruments, scientists discovered that underwater storms caused 20% of the melting in the two glaciers over a nine-month period.
Although accurately quantifying their contribution is difficult due to their chaotic nature, researchers argue that these short-duration processes play an important role in short time intervals.
A worrying vicious circle
The study warns of a positive feedback cycle:
- The eddies melt the ice.
- That melting releases cold, fresh water into the ocean.
- That water mixes with warm, salty water.
- The mix generates more turbulence.
- The turbulence further increases the melting.
“This cycle could intensify in a warmer climate,” noted Lia Siegelman from the Scripps Institution of Oceanography.
Ice shelves play a vital role in containing glaciers and slowing their advance into the ocean. The Thwaites glacier alone contains enough water to raise sea levels by more than 60 centimeters.
Its collapse, acting as a “plug” for the Antarctic ice sheet, could lead to a rise of up to 3 meters in sea levels.
Uncertainties and next steps
Experts acknowledge that there are still great uncertainties, as ice shelves are among the least accessible places on the planet. Studies rely heavily on simulations, which necessitates obtaining more real information.
“Studying these fine-scale oceanic phenomena is the next frontier for understanding ice loss and, ultimately, sea level rise,” stated Siegelman.
The finding about underwater eddies in Antarctica reveals that short-duration oceanic processes can have a significant impact on the melting of key glaciers and, therefore, on the future of global sea level. Understanding these dynamics is essential to anticipate climate change scenarios and design adaptation strategies in the face of a phenomenon that could transform coasts and societies worldwide.
