Antarctic ice sheet: Scientists identify new ‘tipping point’ and warn future sea level rise may be underestimated | CNN

CNN
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Antarctic ice is melting in a new, worrying way, according to a new study. Scientific models used to predict future sea level rise have not taken this development into account, suggesting that current forecasts significantly underestimate the problem.

Scientists from the British Antarctic Survey have found that warm seawater is penetrating beneath the ice sheet at the “grounding line” – the point where the ice rises from the sea floor and begins to float – causing accelerated melting and could lead to a tipping point, according to the report published Tuesday in the journal Nature Geoscience.

A tipping point is the threshold at which a series of small changes accumulate to the point where a system crosses a point of no return.

Melting works like this: relatively warm sea water opens cavities in the ice, allowing more water to enter, leading to more melting and the formation of larger cavities, and so on.

A small increase in ocean temperatures can have a very large impact on the extent of melting, the study found. As climate change warms the oceans, this process accelerates.

“You get this kind of uncontrolled feedback,” said Alex Bradley, an ice dynamics researcher at BAS and lead author of the study. It acts like a tipping point, he told CNN, “where there can be a very sudden change in the amount of melting in these places.”

This tipping point will be impacted by a faster inflow of ice into the oceans, a process not currently accounted for in models of future sea level rise, Bradley said, adding: “Our projections of sea level rise could be significant underestimates.”

According to the study, the consequences would not be felt immediately, but would lead to an even greater rise in sea levels over decades and centuries, threatening coastal communities around the world.

The study does not provide a timeframe for when the tipping point might be reached, nor does it provide figures for how much sea levels are likely to rise. But the region is of enormous importance: the Antarctic ice sheet already loses an average of 150 billion tons of ice every year and, taken as a whole, stores enough water to raise global sea levels by about 58 meters.

The study is not the first to point out Antarctica’s vulnerability to the climate crisis. Numerous research papers point to the vulnerability of West Antarctica in particular, particularly the Thwaites Glacier, also known as the Doomsday Glacier because of its catastrophic impact on sea level rise.

What surprised Bradley about this study, which used climate models to examine how this melting mechanism might affect the entire ice sheet, was that the glaciers in East Antarctica were among the most at risk.

Eric Rignot, a professor of Earth system science at the University of California, Irvine, who was not involved in the research, told CNN the study “encourages us to look more closely at the physical processes that take place in touchdown zones.”

“But this is a very complex, poorly observed region and much more research and field observations are needed,” he warned. This includes determining which processes control the intrusion of seawater under the ice and how exactly this affects ice melting.

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

Ted Scambos, a glaciologist at the University of Colorado Boulder, said the BAS scientists’ new model is “potentially very important” but needs to be considered in the context of new findings, including the mechanisms of ice melting and the effects of tides on pumping seawater beneath the ice.

Bradley hopes the study will spur further research into which regions may be most at risk and provide additional impetus for policy action to combat the climate crisis. “With every small increase in ocean temperature, with every small increase in climate change, we get closer to these tipping points,” he said.