European climate at mercy of retreating sea ice

The "cloud streets" over the Greenland and Iceland seas shown in this satellite image exist as a result of heat and moisture transfer processes that warm the atmosphere and cool the ocean(Credit: G.W.K. Moore)

An international team of scientists has found that retreating sea ice between the Atlantic and Arctic Oceans is linked to weakened air-sea heat exchange in the region. This, it warns, could result in a cooler climate in western Europe and an altered or slower Atlantic Meridional Overturning Circulation (AMOC), which would have knock-on effects for the Gulf Stream and consequently for the atmosphere.

While previous studies have investigated retreating sea ice in the region in terms of marine impact and general trends in ice volume, as well as potential implications for the AMOC as a result of changing salinity, this new research focused on air-sea heat exchange.

The researchers looked at winter data from 1958 to 2014 in their analysis. They found that as sea ice has retreated the area of maximum heat exchange between sea and air has moved too, it occurs at the edge of the sea ice. The locations where warm, dense, salty surface waters sink – as part of the AMOC – have not changed, however, so the heat exchange has weakened (by a magnitude of 20 percent since 1979). This, in turn, could weaken oceanic convection in the Greenland and Iceland seas.

"It's like turning the stove down 20 percent," explains study lead author G.W.K. Moore. "We believe the weakening will continue and eventually cause changes in the Atlantic Meridional Overturning CIrculation and the Gulf Steam, which can impact the climate of Europe."

The research was conducted by an international team from the University of Toronto, University of Bergen, Woods Hole Oceanographic Institution, and University of East Anglia, and is described in a paper published in the journal Nature Climate Change.

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