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The equatorial “SST dipole” represents a mode of climate variability in the tropical Atlantic Ocean that is closely tied to cross-equatorial flow in the atmosphere, from the cold to the warm hemisphere. It has been suggested that this mode is sustained by a positive feedback of the tropical winds on the cross-equatorial SST gradient. The role, if any, of the tropical ocean is the focus of our investigation, which shows that at the latitudes of the SST signal (centered on 10°N/S), there is a weak positive feedback suggested in data from the last ca. half-century, that the cross-equatorial wind stress is closely coupled to this SST gradient on monthly time scales with no discernable lag, that the period Jan.-June is the most active period for coupling. Northward (southward) anomalies of cross-equatorial wind stress are associated with a substantial negative (positive) wind stress curl. This wind system can thus drive a cross-equatorial Sverdrup transport in the ocean from the warm to the cold side of the equator (opposite the winds) with a temporal lag of only a few months. The oceanic observations of sub-surface temperature and a numerical model hindcast also indicate a clear relationship between this mode of wind-driven variability and changes in the zonal transport of the NECC. We estimate that the time-dependent oceanic flow is capable of providing a significant contribution to the damping of the SST dipole, but that external forcing is essential to sustaining the coupled variability.
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