Thermal Expansion in Ocean and Coupled General Circulation Models

Abstract

More than half of the predicted rise in future sea level caused by the enhanced greenhouse effect is currently thought to be due to the thermal expansion of the oceans. Here methods for quantifying this thermal expansion component of sea level rise in ocean general circulation models (GCMs) are developed. A simple linear model of ocean heat uptake allows one to find an expression for the future global trend of sea level rise as a function of globally averaged sea surface temperature. The authors also present a robust procedure for obtaining spatial maps of sea level rise in three-dimensional ocean models. The authors then apply these techniques to the ocean components of three runs of the Commonwealth Scientific and Industrial Research Organisation fully coupled GCM. Two of these experiments have been performed with a recent parameterization of oceanic mesoscale eddies. It is shown that this eddy parameterization significantly lowers ocean heat uptake and future sea level rise in ocean GCMs. For the models running with the new eddy parameterization, the simple linear heat uptake model underestimates the sea level rise found in fully coupled GCMs by approximately 10%.