The basic connection between greenhouse gases, global warming, and rising sea level is well understood, but predicting the exact rate of sea level rise is more difficult. New research appearing in Geophysical Research Letters suggests that current estimates for sea level rise are too conservative because they don’t take Antarctic winds into account (h/t Peter Hannam at The Sydney Morning Herald).
“When we included projected Antarctic wind shifts in a detailed global ocean model, we found water up to 4°C warmer than current temperatures rose up to meet the base of the Antarctic ice shelves,” said lead author Paul Spence from the ARC Centre of Excellence for Climate System Science (ARCCSS) in a statement.
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Wind flows affect ocean currents 700 meters below the surface
What previous models had missed was that changing Antarctic winds alter the flow of oceanic currents down to 700 meters below the surface, and that these changes were enough to bring warmer water into contact with the West Antarctic ice shelf. While the absolute difference of a few degrees Celsius may not seem like a lot, Spence and his colleagues at Australian National University and the University of New South Wales found that it was enough to double the amount of sub-surface warming.
There are also some signs that the newly discovered mechanism may already be at work, as the melt rate of some glaciers in Western Antarctica have recently accelerated more than scientists had expected without any clear explanation.
Results were ‘a shock,’ says lead scientist
“When we first saw the results it was quite a shock. It was one of the few cases where I hoped the science was wrong,” said Spence. “What is particularly concerning is how easy it is for climate change to increase the water temperatures beside Antarctic ice sheets.”
This research also helps explain a number of sudden increases in sea level in the earth’s past by showing that ice shelves are less stable and that melting can accelerate more rapidly than had been thought. Rapid in the context of geological time still means that we are talking about generations, not years, but it also implies that there is less time to get pollution under control.
“Dramatic rises in sea level are almost inevitable if we continue to emit greenhouse gases at the current rate,” says fellow researcher Nicolas Jourdain.