Research Highlights

Nature Reports Climate Change
doi:10.1038/ngeo.2007.3

Sea ice stabilizer

Alex Thompson

J. Clim. 20, 4160–4171 (2007)

© NASA

As the world warms, melting sea ice will stabilize ocean circulation. The ocean thermohaline circulation, a major transporter of heat around the globe, determines much of our present climate. Because this circulation is driven by the sinking of cold dense waters in the northern North Atlantic, it is expected to decrease in strength as the surface ocean warms with climate change, and the extent to which this happens will depend on its initial strength.

Now, Anders Levermann and colleagues at the Potsdam Institute for Climate Impact Research in Germany propose a mechanism for climate-driven changes in the thermohaline circulation that involve the role of sea ice in retaining ocean heat. Based on the results of climate model simulations, they have found that as atmospheric temperatures increase with global warming, melting of sea ice allows more heat to be lost from the ocean, which in turn stabilizes the thermohaline circulation.

This previously unrecognized negative feedback mechanism between sea ice and the thermohaline circulation suggests that in a warmer world, ocean circulation may be more stable than previously thought.