Coastal Altimetry Estimated Currents Compared to Observed Currents from In-Situ Data for the Agulhas Current
Rizopoulou, Konstantina1; Cipollini, Paolo1; Snaith, Helen1; Quartly, Graham2
1National Oceanography Centre Southampton, UNITED KINGDOM; 2Plymouth Marine Laboratory, UNITED KINGDOM
The Agulhas Current (AC) is the western boundary current of the South Indian Ocean and has a crucial role on ocean circulation and climate. In this study AC is observed and characterized by coastal altimetry. Using reprocessed along-track altimeter data with specific data editing and processing strategies, more data can be retrieved near the coast with better spatial coverage and improved quality, compared to standard altimetry datasets. Jason track #96, which crosses the AC nearly orthogonally and on which ACT (Agulhas Current Time-series) array is located, and the ENVISAT track #343, which is also almost coincident with a slightly different orientation, have been used in this study to demonstrate our methodology. Altimeter across-track geostrophic current velocity anomalies are derived from the reprocessed Jason-2 along track sea level anomalies from both PISTACH L2 and eSurge processor (the evolution of the COASTALT processor). These velocities are compared with the ones derived by conventional altimetry RADS (1-Hz) data for both the J-2 and Envisat track as well as the near surface current vector components from the ADCP observations from the ACT cruise. Time-series of geostrophic surface velocity anomalies (GSVA) every 10 days from Jason #96 and a complementary dataset of GSVA’s every 35 days from Envisat are examined. The results indicate the potential usefulness of the along-track altimetry data in contributing to descriptions of surface circulation of western boundary currents and the challenges of such applications on the shelf edge.