Comparisons and contrasts of the
California, Portugal, and Leeuwin Eastern boundary current systems
Mary L. Batteen, Ph.D.
Naval Postgraduate School
Wednesday, February 20, 2002
To investigate the roles of wind forcing, bottom topography, and thermohaline gradients in generating currents and eddies in eastern boundary current (EBC) systems, three EBC regions, the California Current System (CCS), the Northern Canary Current System (NCCS), and the Leeuwin Current System (LCS) are investigated with the use of a fine-resolution numerical model. Results for both the CCS and the NCCS show the generation of classical features on west coasts including coastal equatorward currents and poleward undercurrents, while results for the anomalous LCS show the generation of coastal poleward currents and equatorward undercurrents. While all three regions show highly energetic mesoscale features such as meanders and eddies, only the CCS and the NCCS show the formation of filaments. In the NCCS, many of the classical wind-driven features such as upwelling and filaments are diminished in the Gulf of Cadiz, which is a large embayment that separates the west coast of Portugal from the west coast of Morocco in the NCCS. Meddies (Mediterranean eddies) and the Iberian Current are also formed in the NCCS model, the former due to the presence of Mediterranean Outflow and the latter due to thermohaline gradients. Sensitivity studies, with and without bottom topography, are conducted. Wind forcing (thermohaline gradients) is shown to be the primary mechanism for the generation of currents, meanders, and eddies, while bottom topography is shown to play important roles in intensifying and trapping currents near the coast, in weakening subsurface currents and in intensifying eddies off capes.