The role of the individual air-sea flux components in CO2-induced changes of the ocean's circulation and climate |
| |
Authors: | U Mikolajewicz R Voss |
| |
Institution: | (1) Max-Planck-Institut für Meteorologie, Bundesstr. 55, D-20146 Hamburg, Germany E-mail: mikolajewicz@dkrz.de, DE |
| |
Abstract: | In this study we investigate the role of heat, freshwater and momentum fluxes in changing the oceanic climate and thermohaline
circulation as a consequence of increasing atmospheric CO2 concentration. Two baseline integrations with a fully coupled ocean atmosphere general circulation model with either fixed
or increasing atmospheric CO2 concentrations have been performed. In a set of sensitivity experiments either freshwater (precipitation, evaporation and
runoff from the continents) and/or momentum fluxes were no longer simulated, but prescribed according to one of the fully
coupled baseline experiments. This approach gives a direct estimate of the contribution from the individual flux components.
The direct effect of surface warming and the associated feedbacks in ocean circulation are the dominant processes in weakening
the Atlantic thermohaline circulation in our model. The relative contribution of momentum and freshwater fluxes to the total
response turned out to be less than 25%, each. Changes in atmospheric water vapour transport lead to enhanced freshwater input
into middle and high latitudes, which weakens the overturning. A stronger export of freshwater from the Atlantic drainage
basin to the Indian and Pacific ocean, on the other hand, intensifies the Atlantic overturning circulation. In total the modified
freshwater fluxes slightly weaken the Atlantic thermohaline circulation. The contribution of the modified momentum fluxes
has a similar magnitude, but enhances the formation of North Atlantic deep water. Salinity anomalies in the Atlantic as a
consequence of greenhouse warming stem in almost equal parts from changes in net freshwater fluxes and from changes in ocean
circulation caused by the surface warming due to atmospheric heat fluxes. Important effects of the momentum fluxes are a poleward
shift of the front between Northern Hemisphere subtropical and subpolar gyres and a southward shift in the position of the
Antarctic circumpolar current, with a clear signal in sea level.
Received: 3 May 1999 / Accepted: 11 December 1999 |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|