Combining coastal altimetry and in situ observations to improve Meridional Overturning Circulation estimates: focus on the Southwestern Atlantic
Event: 2019 Ocean Surface Topography Science Team Meeting
Session: Coastal Altimetry
Presentation type: Type Oral
Contribution: PDF file
Since 2009, the Meridional Overturning Circulation (MOC) in the South Atlantic has been observed with arrays of in situ moorings on each side of the basin at 34.5°S. To date, the component of the meridional transport inshore of the shallowest moorings on either side (about 1000 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 portion of the transport that is not directly observed is significant and represents 3 to 4 Sv out of the ~18 Sv total MOC transport at 34.5°S. We aim to use along-track coastal altimetry, combined with existing in situ data, to estimate the unobserved inshore component of the MOC transport at 34.5°S. We first focus on the western edge of the array along South America, evaluating the various coastal altimetry Sea Level Anomaly (SLA) products available by comparison with in situ observations. The resulting best combination of range estimates with atmospheric and geophysical corrections obtained from this comparison will be designated as the reference estimate, while the variability among the various coastal altimetry products will be used as an estimate of the uncertainties in the altimetry estimate. The geostrophic currents derived from the along-track SLA data between the coast and the most inshore mooring will then be used to estimate the missing part of the MOC transport inshore of the mooring array. We will discuss the advantages and limitations of this approach, based on these initial results.