Hamburg 2009 – wissenschaftliches Programm

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SYMU: Marine Umweltphysik

SYMU 2: Marine Umweltphysik II

SYMU 2.1: Hauptvortrag

Mittwoch, 4. März 2009, 17:00–17:30, Physik H II

On the impact of oceanic turbulence on tropical climate variability: Upper ocean diapycnal heat flux and mixing processes in the central and eastern tropical Atlantic — •Marcus Dengler and Rebecca Hummels — Leibniz-Institut für Meereswissenschaften, Kiel, Germany

The ocean has a major influence on tropical Atlantic climate variability. This is most noticeable in the close link between interannual variability of sea surface temperature in the upwelling regions of the tropical Atlantic and variability of rainfall in the counties surrounding the Gulf of Guinea and in northeast Brazil. A key processes controlling sea surface temperature in the upwelling regions is turbulent mixing of water masses just below the mixed layer. Here, we investigate the seasonal variability of upper-ocean mixing processes in the equatorial Atlantic Ocean from microstructure measurements acquired during 6 cruises between September 2005 and 2007. The data set revealed that the upper equatorial Atlantic Ocean is a major mixing hot spot and showed turbulent heat flux to be a dominant term in the mixed layer heat balance. There is, however, a pronounced seasonal cycle in the diapycnal heat flux with maximum values occurring during boreal summer and low values during winter. The processes leading to this variability are discussed. The results suggest that climate models need to accurately model equatorial turbulence to realistically simulate tropical climate variability.