Sack Lunch Seminar (SLS)

Abstract:
The Agulhas leakage transports warm and saline water from the Indian Ocean into the South Atlantic, forming part of the upper returning arm of the meridional overturning circulation (MOC). The variability of Agulhas leakage could thus have an effect on MOC variability and climate. In a high resolution Community Climate Systems Model (CCSM) run, we find that the interannual variability of Agulhas leakage is linked to the equatorial Pacific and El Nino- Southern Oscillation (ENSO). Anomalous wind stress curl forcing over the South Indian Ocean excites westward propagating oceanic Rossby waves that in turn initiate southwestward propagating anomalies along the coast of Africa, which then modulate Agulhas leakage approximately 2 years later. A similar ENSO cycle is detected in an analogous low resolution CCSM run, along with oceanic Rossby wave adjustments to basin-scale wind stress forcing over the South Indian ocean. However, the signal does not propagate into the Agulhas leakage in the low resolution model. Hence, we find that high resolution coupled climate models are necessary to resolve the tropical-subtropical oceanic teleconnection between ENSO and Agulhas leakage variability.