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13th Biennial Challenger Conference for Marine Science8th -11th September 2008 |
Monitoring the Atlantic Overturning Circulation at 26°N
Harry L. Bryden
School of Ocean and Earth Science
University of Southampton
The Atlantic meridional overturning circulation consists of a net northward flow of warm upper ocean waters and a compensating net southward flow of cold deep waters. This circulation transports 1.3 million gigawatts of heat northward across 26°N, heat that is given up to the atmosphere and then carried by westerly winds to Europe. The Rapid programme has been monitoring this meridional overturning circulation at a latitude of 26°N since 2004. Presently we have a 2.5 year time series of the strength and structure of the overturning circulation from which we estimate the average strength of the overturning to be 18.8 Sv with a temporal variability of 5.0 Sv. The Rapid programme offers unique measurements of top-to-bottom temperature and salinity profiles and bottom pressure on a daily basis. Combined with daily measurements of Gulf Stream transport and wind-driven Ekman transport, we have an opportunity to examine the dynamics of the basin-scale ocean circulation. Why is the temporal (subannual) variability in the overturning circulation so small at 26°N? How does the interior ocean adjust to changes in both Gulf Stream flow through Florida Straits and to changes in Ekman transport? These issues will be addressed and some answers provided.