Antarctic ‘Doomsday Glacier’ Could Raise Global Sealevels by More than Two Feet

May 5th, 2021 - by Matthew Taylor / Guardian UK

Study finds more warmer water is reaching Thwaites glacier than was previously believed

Matthew Taylor / Guardian UK

 (May 2, 2021) — An Antarctic glacier larger than the UK is at risk of breaking up after scientists discovered more warm water flowing underneath it than previously thought.

The fate of Thwaites — nicknamed the doomsday glacier — and the massive west Antarctic ice sheet it supports are the biggest unknown factors in future global sea level rise.

Over the past few years, teams of scientists have been crisscrossing the remote and inaccessible region on Antarctica’s western edge to try to understand how fast the ice is melting and what the consequences for the rest of the world might be.

“What happens in west Antarctica is of great societal importance,” said Dr Robert Larter, a scientist with the British Antarctic Survey and principal investigator with the International Thwaites Glacier Collaboration, the most ambitious research project ever carried out in Antarctica. “This is the biggest uncertainty in future sea level rise.”

The ITGC’s $50m research drive has sent teams of scientists to the region to use the latest scientific tools to better understand the speed of the melting and the stability of the glacier.

This month one of the ITCG’s teams, which had managed to get an uncrewed submarine under the front of Thwaites for the first time, published a study showing more relatively warm water was reaching the glacier than previously thought, triggering concerns of faster melting.

Anna Wahlin, a professor of oceanography at the University of Gothenburg who led the study, said the findings suggested that the fate of the glacier and the west Antarctic ice sheet would be sealed in the next two to five years. “The coming years will be crucial … they will determine what happens to this glacier,” she said.

Wahlin said the front of the Thwaites glacier was resting on a number of “pinning points” under the sea. But as relatively warm water from the deep ocean increased the melting, she said, these would be lost, breaking up the ice and allowing warm water further under the ice. This would speed up the flow of the glacier into the sea.

“It could be that once that happens everything falls apart and this is just the beginning of some quite dramatic change … but if it doesn’t happen now I think we can be more confident that it is not going to happen as the worst-case scenarios,” Wahlin said.

The worst-case scenarios for Thwaites are grim. It is the widest glacier on the planet, more than 1km deep and holds enough ice to raise the sea level by 65cm [nearly 26 inches or more than two feet — EAW].

Ice loss has accelerated in the last 30 years and it now contributes about 4% of all global sea level rise. Experts say this could increase dramatically if the ice at the front of Thwaites breaks up, with knock-on effects for other glaciers in the area.

To heighten scientists’ concerns, west Antarctica has been one of the fastest-warming place on Earth in the past 30 years, and since 2000 it has lost more than 1 trillion tons of ice.

Last year, a team of British scientists discovered cavities half the size of the Grand Canyon under Thwaites that, like decay in a tooth, allow warm ocean water to erode the glacier, internally accelerating melting. And because a lot of the ground on which the glacier sits is below sea level, it is thought to be particularly vulnerable to melting as warmer water encroaches further under the ice inland.

Larter said: “The bed gets deeper upstream and there is a glaciological theory that says this is potentially a very unstable situation … it is a very scary scenario when you first hear it, but there are various negative feedback scenarios that might counter it.”

He said if the glacier’s “pinning points” were lost in the next few years it would start to flow faster “and put more ice into the sea”. But he said the question no one could currently answer was exactly how much extra ice will go into the sea if the glacier begins to break up.

“That is a tricky question,” said Larter. “I think I would have to say come back in a couple of years.”

He added: “Nobody knows how it is going to respond to persistent warming — we don’t know because in human history we have never seen it happen. We are trying in every way we can to get a handle on what is going to happen.”

Ella Gilbert, a research scientist at the University of Reading, said what was happening in the polar regions demanded an urgent response from the international community.

“The polar regions are the canary in the coalmine — they are the symbol of climate change,” said Gilbert, who was a joint author of a recent study warning of the catastrophic impact of global heating on Antarctic ice. 

“We really do need to minimise our emissions because if we lose the polar regions, not only are we going to amplify climate change … it will contribute to sea level rise which affects everyone around the globe.”

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