GLOBAL WARMING IN A COUPLED CLIMATE MODEL INCLUDING OCEANIC EDDY-INDUCED ADVECTION

The Gent and McWilliams (GM) parameterization for large-scale water tr ansport caused by mesoscale oceanic eddies is introduced into the ocea nic component of a global coupled ocean-atmosphere model. Parallel sim ulations with and without the GM scheme are performed to examine the e ffect of this parameterization on model behavior under constant atmosp heric CO2 and on the model response to increasing CO2. The control (co nstant CO2) runs show substantial differences in the oceanic stratific ation and extent of convection, similar to differences found previousl y using uncoupled ocean models. The transient (increasing CO2) runs sh ow moderate differences in the rate of oceanic heat sequestration (les s in the GM case), as expected based on passive tracer uptake studies. However, the surface warming is weaker in the GM case, especially ove r the Southern Ocean, which is contrary to some recent supposition. Re asons for the reduced warming in the GM case are discussed.