Data archives from four global coupled ocean-atmosphere models are used
to construct maps of diapycnal mass flux through selected isopycnal
surfaces in the four model oceans. The maps illustrate location and
strength of the up- and downwelling limbs of thermohaline-forced overturning
loops whose stability in the face of rising atmospheric carbon dioxide
(CO$_2$) concentrations is of major concern in century-scale climate
prediction. The up- and downwelling limbs simulated by the four models
for present-day greenhouse gas concentrations are compared with
observational estimates. Predicted changes in the overturning brought
about by gradually rising atmospheric CO$_2$ content are compared
model-to-model. While all models predict some decline in the rate of
Atlantic overturning during CO$_2$-induced global warming, the geographic
layout of the overturning circulations in each model is found to be
insensitive to the changing climate.

Last Updated: 2006-05-06