Coastal Circulation off SW Africa
Event: 2017 Ocean Surface Topography Science Team Meeting
Session: Advances in coastal altimetry: measurement techniques, science applications and synergy with in situ and models
Presentation type: Type Poster
In this new OST-ST project, we are investigating coastal circulation and cross-shelf exchanges along the coast of South Africa. This first study has a focus on the southwest corner of Africa, between 31.5°-36.0°S, 17.0°-20.0°E. The seasonal geostrophic surface circulation anomaly, derived from standard, gridded AVISO SLA products, shows poleward flow in winter and equatorward flow in spring, with a poleward inshore countercurrent that develops during summer in the northern part of the region (north of Cape Town), opposing the local winds. The QUESTION we address here is: IS THIS COUNTERCURRENT REAL? Three approaches are used to answer this question: (1) Coastal tide gauge data are blended with the AVISO gridded data to give more realistic SLA fields in the 50-70km band next to the coast, deriving geostrophic currents from the blended data set; (2) Alongtrack SLA data from the ALES project are examined and compared to standard RADS alongtrack data, to determine whether the improved coverage of ALES provides evidence of the countercurrent; and (3) A realistic numerical circulation model's surface heights and geostrophic currents are analyzed for the same region, using realistic bottom topography and surface winds to drive the model circulation.