Using coastal altimetry to improve Meridional Overturning Circulation estimates in the South Atlantic
Event: 2022 Ocean Surface Topography Science Team Meeting
Session: Science II: Large Scale Ocean Circulation Variability and Change
Presentation type: Type Forum only
Since 2009, the Meridional Overturning Circulation (MOC) in the South Atlantic has been observed with an array of in situ moorings on each side of the basin at 34.5°S, the South Atlantic MOC Basin-wide Array (SAMBA). To date, the component of the meridional transport inshore of the shallowest moorings on either side (about 1300 m depth) has been estimated using a time-mean from an ocean model simulation due to lack of better observations. However, because of their position offshore on the shelf break, the transport that is not directly observed by the SAMBA moorings is expected to be significant. We use along-track coastal altimetry, combined with existing in situ data, to estimate the unobserved inshore component of the MOC transport at 34.5S. This requires designing a method to estimate the geostrophic transport based on surface altimetry data. The analysis of the vertical ocean structure on each side of the SAMBA array, based on available in situ observations, suggests that the currents are mostly barotropic or equivalent barotropic. This property allows for the estimation of the meridional geostrophic transport offshore of the SAMBA array using along-track altimetry. It is found that the northward transport inshore of SAMBA on the Eastern side of the array and the southward transport on the Western side tend to compensate each other on average. However, the variability of the total inshore component (~4 Sv) is not negligible compared to the ~17 Sv total MOC transport at 34.5°S and should be monitored.