J. Clim. http://doi.org/jqb (2012)

Credit: © ISTOCKPHOTO/THINKSTOCK

Increasing atmospheric greenhouse gases are projected to drive large changes in ocean circulation. The ocean currently reduces atmospheric warming through heat and carbon uptake, but the feedback of future circulation changes on global surface temperatures is not well understood.

Michael Winton of the Geophysical Fluid Dynamics Lab and National Ocean and Atmospheric Administration, Princeton, USA, and co-workers used an earth system model to compare the effect of increased carbon dioxide, with and without changes in ocean circulation. Removing circulation changes results in a larger effect on ocean heat storage than on carbon storage. Reduced carbon uptake has a small impact on radiative forcing, while heat transport changes shift heat uptake to higher latitudes, increasing its cooling effect.

They find that changes in ocean circulation could significantly reduce surface warming, especially in the Northern Hemisphere. The circulation changes result in more globally distributed warming, with reduced warming at the subpolar latitudes and increased equatorial warming.