Shelf-break upwelling on a very narrow continental shelf adjacent to a western boundary current formation zone

Abstract

Abstract Two years of hydrodynamic monitoring with an ADCP deployed at 32 m of depth at 12.5°S, in association with remotely sensed and numerical modeling data were used to investigate the uplift forcing mechanisms at the narrowest continental shelf close the formation zone of the South Atlantic western boundary currents (Brazil Current and North Brazil Undercurrent). Fifteen uplift events were successfully identified by shelf-bottom temperature anomalies. Their duration varied between 3 and 21 days, presented negative anomalies as large as 2.8 °C, temperature amplitudes of 4.2 °C, maximum vertical temperature stratification of 3.5 °C. Wind driven processes were the main drivers for most of the mapped uplift events, especially the Ekman transport, second by cyclonic eddies that frequently acted as pre-conditioners for the elevation of the isotherms, associated with 75% of events. Although the lowest absolute temperature associated with the events was relatively high (23.3 °C) due to a depressed regional thermocline, their duration, intensity and vertical extent were consistent with upwelling/uplift events from well-known upwelling regions.