Antarctic ice shelf Larsen C is at risk of collapse due to atmospheric rivers

New research published Thursday shows that these “rivers in the sky” that shed rain and snow as they make landfall are also causing extreme temperatures, surface melt, sea ice breaking and large ocean waves that destabilize ice shelves. The Antarctic Peninsula, a long thin mountain range that points north towards the tip of South America.

These conditions were observed during the collapse of two of the peninsula’s ice shelves, Larsen A and B, in the summers of 1995 and 2002, respectively. And now, as the climate crisis is predicted to warm the Earth even more, the largest remaining ice shelf, Larsen C, is also in danger of total collapse, the study says.

The authors of the study published in Journal of Nature Communication Earth and Environmentused algorithms, climate models and satellite observations to determine that 60% of calving events on the peninsula — when an iceberg breaks off an ice shelf or glacier — were caused by atmospheric rivers between 2000 and 2020.

These ice shelves can destabilize in a variety of ways. For Larsen A, B, and C, foen winds were found—warm, dry air that flows down the mountain after cool, moist air has risen on the other side. This can cause sudden and dramatic temperature changes and, in Antarctica, ice melt. This can have side effects, including cracking ice shelves – the part of the terrestrial ice sheet that protrudes above ocean water.

Melting sea ice also exposes ice shelves to ocean waves, which can cause further destabilization.

“Our study showed that all of these different aspects are actually caused by atmospheric rivers, especially intense ones,” one of the study’s lead authors, Jonathan Ville, from the University of Grenoble-Alpes in France, told CNN.

“And we found that almost all of the truly extreme temperature events that occur in the Antarctic Peninsula occur with atmospheric rivers.”

What does this mean for sea level

The collapse of Larsen C would spell bad news for sea levels around the planet.

Ice shelves break off and can cause sea levels to rise, but they don’t add much volume because they’re already floating in the water. But ice shelves play a critical role in preventing much greater sea level rise.

“Ice shelves keep the glaciers that are on land behind them from flowing into the ocean,” Ville said. “And when these shelves disappear, there is nothing to hold back these glaciers. Their speed increases and they begin to flow into the ocean. And this directly contributes to sea level rise.”

Scientists don’t yet know what the link could be between atmospheric rivers and climate change, but the recent heat wave and conditions in Antarctica at the time were so extreme that experts are beginning to hypothesize that the crisis may have played a role. This will only become clearer if a similar event occurs again in the future.

“The question is whether atmospheric rivers will appear more frequently as the climate changes,” Julien Streuve told CNN. Stroeve, who was not involved in Thursday’s study, is a professor of polar observations and modeling at University College London.

“I think it’s too early to talk about it,” she said, adding that different atmospheric analyzes give different results. “However, it is likely that the atmosphere will play an increasing role in the destruction of ice shelves, weakening them due to surface melt.”

Although the frequency of atmospheric rivers in the future may be unknown, Ville believes that they will at least become more intense, and this may be enough to cause more destabilization.

“It’s pretty simple – as the atmosphere gets warmer, it’s able to hold more moisture, and since an atmospheric river is essentially a moisture transport, that means more moisture can be transported to Antarctica,” he said.

Atmospheric river of moisture will cause storms and tornadoes this week

John Turner, a meteorologist with the British Antarctic Survey, who was also not involved in the study, said that much of the ice shelf’s instability was due to basal melt – melt coming from the bottom – and warned against overemphasizing the role of atmospheric rivers. A study published in the journal Nature found no link between atmospheric rivers and basal melt.

“You need to be careful – there are extreme events for other reasons not related to the river. Sometimes there are strong northerly winds that usually produce a lot of snow and high temperatures that cannot be classified as a river,” he told CNN.

However, Turner agrees that the winds brought by atmospheric rivers could be “the nail in the coffin of some of these ice shelves.”

To imagine what the loss of ice in Antarctica could mean for the world, Turner explained that there is 60 meters – almost 200 feet – of potential sea level rise if the ice on the entire continent melts. West Antarctica, the wider region around the peninsula, is 6 meters (20 feet) high, which would itself swallow entire islands and be a disaster for millions of people living on and off the coast.

Much of the global ice melt and sea level rise so far can be attributed to the melting of the Greenland Ice Sheet in the Arctic.

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