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Interactions Between the Thermohaline Circulation and Tropical Atlantic SST in a Coupled General Circulation ModelTropical Atlantic SST shows a (statistically well-defined) decadal time scale in a 104-year simulation of unforced variability by a coupled general circulation model (CGCM). The SST anomalies superficially resemble observed Tropical Atlantic variability (TAV), and are associated with changes in the atmospheric circulation. Brazilian rainfall is modulated with a decadal time scale, along with the strength of the Atlantic trade winds, which are associated with variations in evaporation and the net surface heat flux. However, in contrast to observed tropical Atlantic variability, the trade winds damp the associated anomalies in ocean temperature, indicating a negative feedback. Tropical SST anomalies in the CGCM, though opposed by the surface heat flux, are advected in from the Southern Hemisphere mid-latitudes. These variations modulate the strength of the thermohaline circulation (THC): warm, salty anomalies at the equator sink drawing cold, fresh mid-latitude water. Upon reaching the equator, the latter inhibit vertical overturning and advection from higher latitudes, which allows warm, salty anomalies to reform, returning the cycle to its original state. Thus, the cycle results from advection of density anomalies and the effect of these anomalies upon the rate of vertical overturning and surface advection. This decadal modulation of Tropical Atlantic SST and the thermohaline circulation is correlated with ocean heat transport to the Northern Hemisphere high latitudes and Norwegian Sea SST. Because of the central role of equatorial convection, we question whether this mechanism is present in the current climate, although we speculate that it may have operated in palaeo times, depending upon the stability of the tropical water column.
Document ID
20010073029
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Miller, Ron
(NASA Goddard Inst. for Space Studies New York, NY United States)
Jiang, Xing-Jian
(NASA Goddard Inst. for Space Studies New York, NY United States)
Travis, Larry
Date Acquired
August 20, 2013
Publication Date
January 29, 2001
Subject Category
Geophysics
Meeting Information
Meeting: US Clivar Atlantic Meeting
Location: Boulder, CO
Country: United States
Start Date: June 12, 2001
End Date: June 14, 2001
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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