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The Antarctic is facing a tipping point where melting glaciers will accelerate and become irreversible, even as global warming slows down, according to research.
A NASA-funded study revealed that the instability of the Thwaites Glacier meant that it would probably arrive at a time when it would be impossible to prevent it from flowing into the sea and triggering a 50-cm rise in sea level. . Other Antarctic glaciers are likely to be also unstable.
Recent research has shown that the rate of ice loss from five Antarctic glaciers had doubled in six years and was five times faster than in the 1990s. Ice losses spread from coast to coast. interior of the continent, with a reduction of more than 100 meters thick on some sites.
The Thwaites Glacier, which is part of the West Antarctic Ice Sheet, is thought to represent the highest risk of a future rapid rise in sea level. Recent Research Published in the Proceedings Journal The National Academy of Sciences revealed that the latter was in danger of succumbing to instability related to the withdrawal of its stranding on the ocean floor, which would cause it to lose ice faster than expected.
Alex Robel, an assistant professor at the US Georgia Institute of Technology and head of the study, said that if instability occurs, the ice cover could disappear in 150 years, even if temperatures stop rising. "It will continue on its own and it's worry," he said.
Modeling simulations suggested a significant ice loss in 600 years, but the researchers said it could happen sooner, depending on the rate of global warming and the nature of the instability.
Hélène Seroussi, a laboratory researcher on NASA jet propulsion, said: "This could happen in the next 200 to 600 years. It depends on the bedrock topography under the ice, and we do not know it in detail yet. "
The Antarctic has nearly eight times more land ice than Greenland and 50 times more than all of the mountain glaciers. The Thwaites Glacier alone contains enough ice to raise the sea level by about 50 cm. The sea level rise associated with warming is already related to the increase in coastal floods and storm surges.
The researchers found that an accurate estimate of the amount of ice that the glacier would lose in the next 50 to 800 years was not possible due to unpredictable climate fluctuations and data limitations. However, 500 simulations of different scenarios showed a loss of stability. This increased uncertainty about future sea-level rise, however, made the worst-case scenario more likely.
A total loss of the Western Antarctic ice sheet is expected to raise sea level by nearly five meters (16 feet), causing the coastal cities of the world to submerge.
A separate study conducted last week in the same newspaper revealed that the extent of the pack ice around Antarctica had dropped "sharply" since 2014. Satellite data showed that Antarctica had lost as much ice sea in four years than the Arctic in 34 years.
Unlike the melting of ice sheets on land, melting sea ice does not raise sea level, but the loss of reflective white ice results in increased absorption of the sun's heat into the ocean. accelerates warming.
Antarctic sea ice has gradually increased over 40 years of measurement and reached a record high in 2014, before falling sharply. The cause of the sudden recovery has not been established.
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