"What's missing from the models used to forecast sea-level rise are critical feedbacks that speed everything up," says Bill Hay, a geologist at the University of Colorado, US. The feedbacks include data on the Arctic Sea ice, the Greenland ice cap, soil moisture and groundwater mining.
"There is an Arctic Sea ice connection," says Hay, adding that melting sea ice -- which is already in the ocean -- does not itself raise sea level. Instead, it plays a role in the overall warming of the Arctic, which leads to ice losses in nearby Greenland and northern Canada.
When sea ice melts, Hay explains, there is an oceanographic effect of releasing more fresh water from the Arctic, which is then replaced by inflows of brinier, warmer water from the south, according to a Colorado statement. "It's a big heat pump that brings heat to the Arctic but that's not in any of the models," says the geologist.
The warmer water pushes the Arctic toward more ice-free waters, which absorb sunlight rather than reflect it back into space like sea ice does. The more open water there is, the more heat is trapped in the Arctic waters, and the warmer things can get.
Then there are gigantic stores of ice in Greenland and Antarctica. During the last interglacial period, sea level rose 10 metres due to the melting of all that ice -- without any help from humans, says Hay. New data suggests that the sea-level rise in the oceans took place over a few centuries, according to Hay...
Reynisfjara with Dyrhólaey. Vík, Iceland [2008], shot by Rosino, Wikimedia Commons via Flickr, under the Creative Commons Attribution-Share Alike 2.0 Generic license.
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