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The Role of the Wind in Maintaining the Ocean's Thermohaline Circulation
Timmermann, A. and Goosse, H.  2004.  Is the wind stress forcing essential for the meriodional overturning circulation?  Geophysical Research Letters 31: 10.1029/2003GL018777.

Climate alarmists have been stirring a pot of preposterous propositions in the wake of a report prepared for Pentagon strategic planners that considers the climatic consequences of a significant slowdown of the Atlantic branch of the ocean's thermohaline circulation, which is suggested by some models to be forced by the historical and projected future rise in the air's CO2 content (Stipp, 2004).  In a pair of recent Journal Reviews, we have highlighted the opposing modeling work of Wu et al. (2004) and Bleck and Sun (2004) that refutes this scenario, and we here review another such study.

What was done
Timmermann and Goosse used a global coupled atmosphere-ocean sea-ice model of intermediate complexity (ECBilt-Clio), which has been described extensively by Opsteegh et al. (1998), Goosse and Fichefet (1999) and Goosse et al. (2002), to study the role of the wind in maintaining the meriodional overturning circulation in the Atlantic Ocean.

What was learned
The two scientists say they determined that "wind-forcing is a crucial element to sustain meriodional overturning flow in the Atlantic," and that their general conclusion "is consistent with the findings of Oka et al. (2001)."  In addition, they state that "density gradients needed to drive thermohaline flow can not be maintained without wind-forcing," noting that "the wind-driven circulation is a pre-requisite for the set-up of meriodional overturning flow in the North Atlantic."

What it means
Timmermann and Goosse conclude by saying that "state-of-the-art models do not agree on the prediction of the future evolution of the intensity of the thermohaline circulation."  The most recent work in the field, however, i.e., theirs and that of Bleck and Sun (2004) and Wu et al. (2004), strongly suggests that a dramatic CO2-induced slowdown of the Gulf Stream seems so highly unlikely that those who hype it as lying just around the corner do science, themselves and everyone else a great disservice.

Bleck, R. and Sun, S.  2004.  Diagnostics of the oceanic thermohaline circulation in a coupled climate model.  Global and Planetary Change 40: 233-248.

Goosse, H. and Fichefet, T.  1999.  Importance of ice-ocean interactions for the global ocean circulation: A model study.  Journal of Geophysical Research 104: 23,337-23,356.

Goosse, H., Selten, F.M., Haarsma, R.J. and Opsteegh, J.D.  2002.  Large sea-ice volume anomalies simulated in a coupled climate model.  Climate Dynamics 10: 10.1007/s0382-002-0290-2.

Oka, A., Hasumi, H. and Suginohara, N.  2001.  Stabilization of thermohaline circulation by wind-driven and vertical diffusive salt transport.  Climate Dynamics 18: 71-83.

Opsteegh, J.D., Haarsma, R.J., Selten, F.M. and Kattenberg, A.  1998.  ECBILT: A dynamic alternative to mixed boundary conditions in ocean models.  Tellus 50A: 348-367.

Stipp, D.  2004.  Climate Collapse: The Pentagon's Weather Niare.  Fortune, 26 Jan 2004 (,15114,582584,00l?cn).

Wu, P., Wood, R. and Stott, P.  2004.  Does the recent freshening trend in the North Atlantic indicate a weakening thermohaline circulation?  Geophysical Research Letters 31: 10.1029/2003GL018584.

Reviewed 5 May 2004