Interannual Variability of Antarctic Intermediate Water in the Tropical North Atlantic

Abstract Interannual variability of Antarctic Intermediate Water (AAIW) in the tropical North Atlantic is investigated using the GECCO2 ocean state estimate and Argo data. AAIW salinity variability near the western boundary is highly correlated with the transport along the western boundary on interannual timescales. Northward propagating anomalies are associated with the western boundary transport variability that, to some extent, is related to the large‐scale wind stress curl forcing by means of the Sverdrup balance. AAIW anomalies also propagate westward with the speed of baroclinic Rossby waves, indicating that the displacement of the meridional salinity gradient by westward propagation of baroclinic Rossby waves plays a role in the variability of AAIW characteristics. Slower eastward spreading of AAIW anomalies is identified on decadal timescales likely associated with the advection of salinity anomalies by weak eastward current bands. Understanding the observed interannual and decadal variability of AAIW salinity is important to properly interpret salinity changes reported in response to changes in the hydrological cycle.