Understanding Tropical Atlantic Warming over the Last Decades
Starts 14 Mar 2019 11:00
Ends 14 Mar 2019 12:30
Central European Time
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The tropical Atlantic has warmed in recent decades, in particular in the equatorial and coastal upwelling regions. This warming was not directly forced by local heat exchange with the atmosphere, and also wind stress in the tropical Atlantic that drives oceanic upwelling rather increased than decreased. Remote forcing from outside the tropical Atlantic might thus have played a role.
In this presentation, the contribution of different potential drivers is assessed utilizing a series of hindcast and sensitivity experiments with a high-resolution ocean model. It is shown that both an increase in the inflow of warm Indian Ocean waters through Agulhas leakage and a slowdown of the Atlantic Meridional Overturning Circulation (AMOC) can lead to a general warming in the tropical Atlantic ocean.
Compared to a control simulation, an experiment in which Agulhas leakage was artificially increased by strengthening the Southern Hemisphere Westerlies shows a pronounced warming trend in the upper tropical Atlantic Ocean. The SST pattern that arises in response to an idealized slowdown of the AMOC due to enhanced freshwater input around Greenland is reminiscent of the observed warming trend. In this context, the role of the Atlantic subtropical-tropical cells (STCs) and in particular the strengthening of the northern cell is discussed. Mean pathways and transports between the subtropical and tropical Atlantic Ocean are also inferred from Argo observations for the last decade.
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