Robert Larter
Thwaites Glacier in West Antarctica in 2019. A new study suggests that warm
CNN
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The Antarctic ice sheet is melting in a new, troubling way that scientific models used to project future sea level rise didn’t take into account, suggesting that current projections could be significantly underestimating the problem, according to a new study.
Scientists from the British Antarctic Survey have found that warm ocean water is seeping under the ice sheet at its “grounding line” – the point at which the ice rises from the sea floor and begins to float – causing accelerated melting that could lead to a tipping point . according to a 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 the system past the point of no return.
Melting works like this: the relatively warm ocean water opens up voids in the ice, allowing more water to seep in, which causes more melting and the creation of larger voids, and so on.
The study found that a small increase in ocean temperatures can have a very large impact on the amount of melting. As climate change warms the oceans, the process is accelerating.
“You get this kind of feedback,” said Alex Bradley, an ice dynamics researcher at BAS and lead author of the paper. It acts like a tipping point, he told CNN, “where you can have a very sudden shift in how much melting is going on in these places.”
That tipping point would see ice flow faster into the oceans, a process not currently included in models of future sea level rise, Bradley said, suggesting that “our sea level rise projections may be significantly underestimated,” he added.
The effects wouldn’t be immediate, the study said, but there would be more sea-level rise that would accumulate over decades and hundreds of years, threatening coastal communities around the world.
The study does not provide time frames for when a tipping point might be reached, nor does it provide data on how much sea level rise can be expected. But the area is hugely significant: the Antarctic ice sheet already sheds an average of 150 billion metric tons of ice annually, and as a whole holds 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 number of studies point to the vulnerability of West Antarctica in particular, particularly the Thwaites Glacier, known as the doomsday glacier, for the catastrophic impact it could have on sea level rise.
But what surprised Bradley about the study, which used climate modeling to understand how this melting mechanism could affect the entire ice sheet, is that some of the most vulnerable glaciers were those in East Antarctica.
Sebnem Coskun/Anadolu/Getty Images
Glaciers in Antarctica on February 8, 2024. Much research has examined the vulnerability of this vast continent to the effects of the climate crisis.
Eric Rignot, a professor of Earth systems science at the University of California, Irvine, who was not involved in the research, told CNN that the study “encourages us to take a closer look at the physical processes occurring in grounding zones.”
“But it’s a very complex, poorly observed area, and a lot more research and field observations are needed,” he warned, including finding out what processes control seawater intrusion under the ice and exactly how it affects ice melting.
Recent research from West Antarctica found that melting at the base of the glaciers was actually lower than expected because it was being suppressed by a layer of cooler, 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 needs to be looked at alongside more recent findings, including the mechanisms of ice melt and tidal effects. they have for pumping sea water under the ice.
Bradley hopes the study will spur further research into which regions could be most at risk, and give policymakers further impetus to tackle the climate crisis. “With every little increase in ocean temperature, with every little increase in climate change, we’re getting closer to these tipping points,” he said.