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First evidence that human-induced global warming has led to melting of West Antarctic Ice Sheet




The first evidence of a direct link between human-induced global warming and the melting of the West Antarctic Ice Sheet was published on Monday.

The Cambridge-based British Antarctic Survey and researchers in the US said their findings show that curbing greenhouse gas emissions now could reduce the future contribution the region makes to a global rise in sea levels.

Aerial view of Getz ice shelf calving front (western Amundsen Sea, West Antarctica) taken from a helicopter after deploying Autonomous Phase Sensitive radar on the ice to measure ocean-driven ice shelf melt continuously. Picture: Pierre Dutrieux / BAS (15018267)
Aerial view of Getz ice shelf calving front (western Amundsen Sea, West Antarctica) taken from a helicopter after deploying Autonomous Phase Sensitive radar on the ice to measure ocean-driven ice shelf melt continuously. Picture: Pierre Dutrieux / BAS (15018267)

Their study, published in the journal Nature Geoscience, combined satellite observations and climate model simulations to understand how winds over the ocean near West Antarctica have changed since the 1920s.

There has been a significant increase in ice loss in West Antarctica in the last few decades.

Scientists have already proved that warmer sea temperatures have caused glaciers to melt, and that varying winds in the region cause transitions between relatively warm and cool ocean conditions around key glaciers.

But it was not clear how these wind variations could cause an ongoing loss of ice.

The team found that in addition to natural variations that last about a decade, a longer-term change in the winds can be linked to human activities, and warmer oceans conditions have been the result.

View of Dotson ice shelf calving front (western Amundsen Sea, West Antarctica) taken aboard the R/V Nathaniel B. Palmer after deploying the autonomous underwater vehicle Autosub3 under Pine Island ice shelf. Picture: Pierre Dutrieux / BAS (15018265)
View of Dotson ice shelf calving front (western Amundsen Sea, West Antarctica) taken aboard the R/V Nathaniel B. Palmer after deploying the autonomous underwater vehicle Autosub3 under Pine Island ice shelf. Picture: Pierre Dutrieux / BAS (15018265)

Lead author Professor Paul Holland, from the British Antarctic Survey, says: “The impact of human-induced climate change on the West Antarctic Ice Sheet is not simple. This is the first evidence for a direct link between human activities and the loss of ice from West Antarctica.

“Our results imply that a combination of human activity and natural climate variations have caused ice loss in this region, accounting for around 4.5cm of sea-level rise per century.”

The team simulated future winds using modelling.

“An important finding is that if high greenhouse-gas emissions continue in future, the winds keep changing and there could be a further increase in ice melting,” says Prof Holland. “However, if emissions of greenhouse gases are curtailed, there is little change in the winds from present-day conditions. This shows that curbing greenhouse gas emissions now could reduce the future sea-level contribution from this region.”

Co-author Prof Pierre Dutrieux from Lamont-Doherty Earth Observatory, Columbia University Earth Institute in New York, adds: “We knew this region was affected by natural climate cycles lasting about a decade, but these didn’t necessarily explain the ice loss.Now we have evidence that a century-long change underlies these cycles, and that it is caused by human activities.”

View of Pine Island ice shelf calving front (eastern Amundsen Sea, West Antarctica) taken aboard the R/V Nathaniel B. Palmer after deploying the autonomous underwater vehicle Autosub3 under the ice. Picture: Pierre Dutrieux / BAS (15018269)
View of Pine Island ice shelf calving front (eastern Amundsen Sea, West Antarctica) taken aboard the R/V Nathaniel B. Palmer after deploying the autonomous underwater vehicle Autosub3 under the ice. Picture: Pierre Dutrieux / BAS (15018269)

Prof Eric Steig, a co-author from the University of Washington, says: “These results solve a long-standing puzzle. We have known for some time that varying winds near the West Antarctic Ice Sheet have contributed to the ice loss, but it has not been clear why the ice sheet is changing now.

“Our work with ice cores drilled in the Antarctic Ice Sheet have shown, for example, that wind conditions have been similar in the past. But the ice core data also suggest a subtle long-term trend in the winds.

“This new work corroborates that evidence and, furthermore, explains why that trend has occurred.”

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