EVIDENCE OF A SPORADIC NORTHWARD FLOW OF INTERMEDIATE WATERS ALONG THE WESTERN SOUTH ATLANTIC CONTINENTAL SLOPE AT 34ºS: SEASONAL AND INTER-ANNUAL VARIABILITY

BAQUES, MICHELE; BERDEN GIULIANA; DAVILA, PAOLA; CHARO, MARCELA; PIOLA, ALBERTO R.

Congreso; Ocean Science Meeting; 2022

AGU, ASLO, The Oceanography Society

Intermediate Waters (IW) in the Western South Atlantic Ocean (WSAO) play a crucial role in the Atlantic Meridional Overturning Circulation (AMOC) as they contribute to compensate the export of North Atlantic Deep Water to other ocean basins. The low salinity (<34.3) and high oxygen concentration (>196 μmol/kg) IW flow northward at intermediate depths along the Patagonian continental slope within the Malvinas Current (MC). Near 38ºS the MC encounters the southward flowing Brazil Current and both currents veer offshore. The main pathway of IW into the North Atlantic Ocean is through the subtropical gyre, which transports a salty variety of IW after mixing with IW derived from the Indian Ocean in the Cape Basin. Previous studies suggest that a minor portion of the MC extends north of the Brazil-Malvinas Confluence until 36ºS along the continental slope of South America between 600 and 800 m depth. Based on oceanographic observations and numerical modeling, here we present new evidence of a narrow band of fresh IW extending northward past the Brazil-Malvinas Confluence to about 34ºS. This flow resembles the AAIW path originally proposed by Wüst (1395) based mainly on a thermohaline rather than a wind-driven circulation. We investigate the probability of occurrence of this phenomenon, the possible driving mechanisms and its seasonal and inter-annual  variability. Our results indicate that, even though this flow is weak, with measured velocities lower than 25 cm.s-1, and has occasional intense pulses, it might be a direct pathway for IW from its origin in the subpolar region to near 34ºS.