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Ice Sheet Instability: Is All of West Antarctica at Risk?

The whole West Antarctic ice sheet may become unstable. In 2015, several studies reported that one region, the Amundsen sector, had been destabilized—meaning it will now discharge its ice into the oceans at increasing rates. Together, the glaciers of this region transport as much ice to the ocean as all the glaciers of Greenland; if all the ice contained in them reaches the ocean, it could increase sea levels by as much as a meter. This would be a major problem for many coastal cities around the world, but they could take steps to prepare. The bigger question on Dr. Matthias Mengel’s mind is this: Could the Amundsen instability trigger the collapse of the entire West Antarctic ice sheet? The potential sea level increase could make it impossible for coastal regions to adapt. It has happened before in the history of the Earth, and it could happen again. To assess the risk, Dr. Mengel first needs to understand the dynamics of Antarctica’s ice and how much climate change is likely to affect it.
Previous work on this topic involved small-scale, regional studies. The computer models available required the Amundsen sector to be analyzed alone, artificially extracted from its surroundings. In reality, the different zones of the West Antarctic ice sheet are interconnected and the collapse of one will alter the direction of ice flow and the boundaries between them. Dr. Mengel is armed with a continent-scale model, which is unique in its ability to handle the entire ice sheet. By adjusting it to the specific parameters of the region, he will be able to answer questions about how the ice sheet flows after breakdowns of smaller parts and how it may change with time and a warming planet.
The current loss of the Antarctic ice sheets, their thinning and retreat, has been driven by an increase in the warm water flowing towards the Amundsen ice shelves. These are the portions of the glaciers that extend, floating, into the sea. As they melt, it reduces the pressure on the ice behind them, which accelerates and thins, in turn. This can trigger a feedback loop, which, once started, can lead to the disintegration of the entire ice sheet. The phenomenon is aided by the underlying bedrock being grounded deeply below sea level; it would be ocean floor if there were no ice. Most of the West Antarctic ice sheet meets the criteria of bedrock below sea level.
Once part of an ice sheet has been destabilized, sea-level rise is inevitable. What makes this situation especially hard to manage is the uncertainty around the question “How much?” As Dr. Mengel says, every centimeter is a bad centimeter, increasing damage to low-lying areas, but his results on the contribution to expect from Antarctic ice discharge should provide valuable, concrete numbers for mitigation and adaptation efforts. He’ll also share his open-source model online so that other researchers can adapt it to their contexts and better understand ice dynamics around the world. More than 150 million people live in areas that would be impacted by one meter of sea-level rise. For them, including the populations of many small island states and low-lying developing countries, Dr. Mengel’s results could provide key data to push for stronger climate change policies that will help limit the waters’ rise.

Scientific title: Will The Entire West Antarctic Ice Sheet Destabilize And Contribute To The Global Sea-Level Rise
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Potsdam-Institut für Klimafolgenforschung e.V.





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