Cross-Shelf Exchange in the Southwestern Atlantic Shelf: Climatology and Extreme Events

BERDEN, GIULIANA; PIOLA, ALBERTO R.; PALMA, ELBIO

Virtual

Congreso; Ocean Science Meeting; 2022

AGU, ASLO, The Oceanography Society

The western South Atlantic shelf hosts one of the most productive marine ecosystems of the southern hemisphere due to the supply of nutrients from continental discharge (Río de la Plata estuary), shelf currents and open ocean sources. The export of productive shelf waters modulates the primary productivity over the shelf and has a significant biogeochemical impact on the open ocean. The Brazil and Malvinas Currents flow in opposite directions along the shelf edge and collide near 37.5°S forming the Brazil/Malvinas Confluence (BMC). These strong currents act as barriers to exchanges between the adjacent shelf and the open ocean. However, in-situ and satellite data, and numerical models suggest intense cross-shelf transports near the BMC. Here, we use a high-resolution global reanalysis to study the export of shelf water between 30-40°S (TrOff) during 1993-2018. The model indicates that the most favorable paths of export from the shelf are located near the BMC and at 32.25°S and a net time-averaged offshore transport of 2.09 Sv. TrOff presents a weak seasonal variability, with a maximum in austral summer, and high standard deviation in intra-monthly variability. TrOff variability is mainly associated with the local winds in response to synoptic atmospheric systems. Extreme events of TrOff are more frequent in fall and spring, and less frequent in summer. The export events typically last less than 2 days, and the maximum offshore transport reaches 9.45 Sv.