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New link between greenhouse gases and sea level rise

A new study provides the first evidence that rising greenhouse gases are having a long-term warming effect on the Amundsen Sea in West Antarctica. British Antarctic Survey (BAS) scientists say that while others have proposed this link, no one has been able to demonstrate it.

The loss of ice from the West Antarctic Ice Sheet into the Amundsen Sea is one of the most increasing and concerning contributions to sea level rise globally. If the West Antarctic ice sheet were to melt, global sea levels could rise by up to 3 meters. Models of ice loss suggest the ocean may have warmed in the Amundsen Sea over the past hundred years, but scientific observations of the area didn’t begin until 1994.

In the study—published in the journal Geophysical Research Letters—oceanographers used advanced computer modeling to simulate the ocean’s response to a range of possible changes in the atmosphere between 1920 and 2013.

Simulations show that the Amundsen Sea has generally warmed over the century. This warming is consistent with simulated trends in wind patterns in the region that increase temperatures by driving currents of warm water towards and under the ice. Increasing greenhouse gases are known to make these wind patterns more likely, and so the trend in winds is thought to be caused in part by human activity.

This study supports theories that ocean temperatures in the Amundsen Sea have increased since before records began. It also provides the missing link between ocean warming and wind trends, which are known to be partly driven by greenhouse gases. Ocean temperatures around the West Antarctic Ice Sheet are likely to continue to rise if greenhouse gas emissions increase, with consequences for ice melt and global sea levels. These results, however, suggest that this trend could be halted if emissions are sufficiently reduced and wind patterns in the region are stabilized.

Dr Kaitlin Naughten, ocean ice modeler at BAS and lead author of this study, says: “Our simulations show how the Amundsen Sea responds to long-term trends in the atmosphere, in particular westerly winds from the ‘southern hemisphere. This raises concerns for the future as we know these winds are affected by greenhouse gases. However, it should also give us hope, as it shows that sea level rise is not beyond our control.

Professor Paul Holland, BAS ocean and ice specialist and co-author of the study, says: “Changes in Southern Hemisphere westerly winds are a well-established climate response to the effect of greenhouse gas. However, the Amundsen Sea is also subject to very high natural climate variability. Simulations suggest that both natural and anthropogenic changes are responsible for ocean-induced ice loss from the West Antarctic Ice Sheet.

– This press release was originally published on the UK Antarctic Survey website