Antarctic ice sheet: scientists identify new ‘tipping point’ that may underestimate future sea level rise | CNN

CNN
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The Antarctic ice sheet is melting in a new, worrying way that scientific models used to project future sea level rise have not taken into account. This suggests that current projections could significantly underestimate the problem, according to a new study.

Scientists from the British Antarctic Survey found that warm ocean water seeps under the ice sheet at the ‘grounding line’ – the point at which ice rises from the seabed and begins to float – causing accelerated melting, which could lead to a tipping point. according to the report published Tuesday in the journal Nature Geoscience.

A tipping point refers to the threshold at which a series of small changes accumulate to push a system past a point of no return.

The melting works like this: relatively warm ocean water opens voids in the ice, allowing more water to seep in, causing more melting and larger voids, and so on.

A small increase in ocean temperature can have a very big impact on the rate of melting, the study shows. As climate change warms the oceans, the process is accelerating.

“You get this kind of runaway feedback,” says Alex Bradley, an ice dynamics researcher at BAS and lead author of the paper. It’s acting like a tipping point, he told CNN, “where you can see a very sudden change in the rate of melting in these places.”

This tipping point would come about through faster ice flow into the oceans, in a process not currently included in models of future sea level rise, Bradley said, suggesting that “our projections of sea level rise could be a significant underestimate,” he added to.

The implications would not be felt immediately, according to the study, but there would be increased sea level rise over decades and hundreds of years, threatening coastal communities around the world.

The study does not provide time frames for when the tipping point could be reached, nor does it provide figures on how much sea level rise can be expected. But the region is hugely important: The Antarctic ice sheet already sheds an average of 150 billion tons of ice each year and, in its entirety, contains enough water to raise global sea levels by about 190 feet (about 58 meters).

The study is not the first to highlight Antarctica’s vulnerability to the climate crisis. A raft of studies point to the vulnerability of West Antarctica in particular, and in particular the Thwaites Glacier, known as the Doomsday Glacier because of the catastrophic impact it could have on sea level rise.

But what surprised Bradley about this study, which used climate models to understand how this melting mechanism could affect the entire ice sheet, is that some of the most vulnerable glaciers were those of East Antarctica.

Eric Rignot, a professor of Earth system sciences at the University of California, Irvine, who was not involved in the study, told CNN that the study “encourages us to take a closer look at the physical processes that occur in Earth zones.”

“But this is a very complex, poorly observed region and much more research and field observations are needed,” he warned, including identifying what processes control the intrusion of ocean water under the ice and how exactly this is driving the melting of the ice affects.

Recent research from West Antarctica found that melting at the base of glaciers was actually lower than expected because it was suppressed by a layer of colder, fresher water – although scientists still found rapid retreat.

Ted Scambos, a glaciologist at the University of Colorado Boulder, said the new model developed by the BAS scientists is “potentially very important” but should be viewed together with more recent findings, including mechanisms of ice melt and the consequences for the tides. involve pumping seawater under the ice.

Bradley hopes the study will spark more research into which regions are most at risk and provide further impetus for policies to tackle the climate crisis. “Every little increase in ocean temperature, every little increase in climate change, we get closer to these tipping points,” he said.