Ancient Antarctic ice melt caused dramatic sea level rise - and researchers warn it could happen again

A global research team including Keele University’s Professor Chris Fogwill, Head of the School of Geography, Geology and Environment, have warned that increasing ocean temperatures could trigger a dramatic rise in sea levels, after uncovering evidence of a similar event more than 100,000 years ago.

At present, the consensus of the Intergovernmental Panel on Climate Change (IPCC) 2013 report suggests that global sea level will rise between 40cm and 80cm over the next century, with Antarctica only contributing around 5cm of this total. But the researchers are now concerned that Antarctica’s contribution could be up to ten times greater than previously thought.

The new research, published in the Proceedings of the National Academy of Sciences (PNAS) journal, found that a mass melting of the West Antarctic Ice Sheet caused by less than 2°C of ocean warming resulted in sea levels rising by more than three metres during a period known as the “last interglacial”.

This occurred between 116,000 and 129,000 years ago, with the scientists pinpointing the time of the mass melting by studying fine layers of ancient volcanic ash in the ice. Analysis like this is normally conducted by drilling down into the ice core to extract samples, but this team used a different method – horizontal ice core analysis.

Alarmingly, the data showed that most of the ice loss occurred within the first 1,000 years of the last interglacial, showing how sensitive the Antarctic is to a rise in temperatures, and the researchers warned that we could be close to a similar tipping point today with global warming meaning that ocean temperatures are rising faster than expected.

Professor Chris Fogwill, Director of Keele University’s Institute for Sustainable Futures, said: “Recent projections suggest that the Antarctic contribution may be up to ten times higher than the United Nations’ IPCC forecast, which is deeply worrying.

“Our study highlights that the Antarctic ice sheet may lie close to a tipping point, which once passed may commit us to rapid sea level rise for millennia to come. This highlights the urgent need to reduce and control greenhouse gas emissions that are driving warming today.”

Lead author Professor Chris Turney from the University of New South Wales, Australia, added: “The Paris Climate Agreement commits to restricting global warming to 2˚C, ideally 1.5˚C, this century. Our findings show that we don’t want to get close to 2˚C warming.”

The researchers now plan to expand the research to assess just how quickly the West Antarctic Ice Sheet responded to the warming, and which areas were first affected.

Professor Turney added: “We only tested one location, so we don’t know whether it was the first sector of Antarctica that melted, or whether it melted relatively late. How these changes in Antarctica impacted the rest of the world remains a huge unknown as the planet warms into the future.

“Testing other locations will give us a better idea for the areas we really need to monitor as the planet continues to warm.”

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