Climate Change

Troubling picture of Antarctica ice shelves: Study finds 40% volume lost in 25 years

Half of them shrinking with no sign of recovery, about 7.5 trillion tonnes of meltwater released into oceans

 
By Rohini Krishnamurthy
Published: Friday 13 October 2023
Scientists examined 162 ice shelves and found that 71 lost mass. Photo: iStock__

A new study has highlighted a troubling picture of Antarctica’s ice shelves. The most vulnerable parts of the Antarctic ice sheet may have lost 40 per cent of their volume in the last 25 years, between 1997 and 2021, it has found. 

Ice shelves are floating pieces of ice connected to a landmass. Out of 162 ice shelves, 71 lost mass, releasing some 7.5 trillion tonnes of meltwater into the oceans, the study published in the journal Science Advances noted.

“We expected most ice shelves to go through cycles of rapid, but short-lived shrinking, then to regrow slowly. Instead, we see that almost half of them are shrinking with no sign of recovery,” Benjamin Davison, a research fellow at the University of Leeds and the study’s author, said in a statement.


Read more: Antarctic iceberg, once Earth’s biggest, suffers major split


Ice shelves experience widespread and often intense surface melting, the paper said.

Scientists predicted that ice shelf surface melting is likely to intensify this century. They could disintegrate due to multiple factors, such as changes in sea-ice conditions, ocean swell (regular movement of waves up and down in the open sea generated by wind), currents and tides.

Davison and his colleagues analysed over 100,000 satellite radar images to examine the “state of the health” of ice shelves from 1997 to 2021.

The researchers found the Antarctic ice shelves released roughly 67,000 billion tonnes of freshwater to the Southern Ocean from 1997 to 2021, on average. Some 60 per cent was probably due to calving — where large chunks of ice separate from the shelf and move into the ocean.

Ice shelf mass loss was concentrated along the Antarctic Peninsula, the Amundsen Sea, and Bellingshausen Sea in West Antarctica and in Wilkes Land and Victoria Land in East Antarctica, the researchers found.


Read more: Close shave: Giant iceberg grazes Antarctica’s Brunt Ice Shelf


Of the 162 ice shelves, 29 gained mass and 62 did not see a significant change in mass. These ice shelves are mostly concentrated in Dronning Maud Land, the eastern Weddell Sea coastline, and around the Amery Ice Shelf, the study found.

Between 1997 and 2002, the researchers observed a rapid decrease in Antarctic ice shelf mass. But from 2002 to 2021, there was some mass gain as some ice shelves — Ronne, Filchner, Amery and Cook — advanced.

This, however, did not indicate that ice shelves are recovering, the paper explained. Some 68 ice shelves showed a significant loss from 1997 to 2021. Of them, 26 saw a reduction of two per cent annually and 47 lost more than 30 per cent of their mass since 1997.

Some ice shelves contributed a lot more than the rest. For example, the Getz Ice Shelf lost 1.9 trillion tonnes of ice during the last 25 years. Calving was responsible for five per cent of the loss. The rest was due to melting at the base of the ice shelf due to the warming ocean.


Read more: On the move: Antarctic iceberg the size of Greater London breaks away


Additionally, the researchers saw a pattern. The ice shelves in western Antarctica experienced ice loss while most on the eastern side stayed the same or gained mass.

“There is a mixed picture of ice-shelf deterioration, and this is to do with the ocean temperature and ocean currents around Antarctica,” Davison explained.

He explained that the western half is exposed to warm water, thereby quickly eroding the ice shelves from the bottom. East Antarctica, on the other hand, is protected by a band of cold water lines the coast, shielding it from the nearby warm water.

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