Hydrographic conditions in the Brazil‐Malvinas Confluence during austral summer 1990

• Published in: Journal of Geophysical Research
• Main Authors: Provost, Christine, Gana, S, Garcon, V, Maamaatuaiahutapu, K, England, Mh
• Format: Article in Journal/Newspaper
• Language: English
• Published: Amer Geophysical Union 1995
• Subjects: Austral; NADW; North Atlantic Deep Water; North Atlantic
• Online Access: https://archimer.ifremer.fr/doc/00481/59318/62077.pdf; https://doi.org/10.1029/94JC02864; https://archimer.ifremer.fr/doc/00481/59318/

The Confluence 3 cruise during February 1990 provides the first hydrographic survey of the Brazil-Malvinas Confluence region ever obtained with such a refined spatial resolution over the continental slope. The closely spaced stations on the slope permit the observation of the branching of the Malvinas Current near 40 degrees S. The eastern branch returns south, while the eastern one is squeezed along the continental slope, managing to continue northward as far north as 36.3 degrees S. The Brazil-Malvinas (B-M) front has a north-south orientation on the slope and an east-west direction offshore. The B-M front is marked by very strong gradients in temperature and salinity. Fine scale vertical structures and intrusions are numerous in the vicinity of the front and cover a wide range of scales. The largest intrusion observed is a 50-km-wide, 350-m-thick subsurface lense of Thermocline Water present on the Malvinas side of the front. The fine scale vertical structure results in very high temperature and salinity fluxes across the front of the order of 2 x 10(-2)degrees C m(-1) s(-1) and 10(-3) psu m(-1) s(-1). Two types of mode waters are identified as follows: Subtropical Mode Waters north of the front and Subantarctic Mode Waters on both sides of the front. The Subantarctic mode waters (SAMW) appear to recirculate near the western boundary. A young variety of SAMW (lighter, very oxygenated) propagates northward along the continental slope with the Malvinas Current. It detaches from the coast near 37 degrees S and is strongly altered in the frontal region. It is then entrained southward with the Malvinas return flow and Brazil Current extension. The Confluence 3 hydrographic survey provides a good description of the North Atlantic Deep Water (NADW) and Circumpolar Deep Water (CDW) convergence near the western boundary. Strong, fine scale vertical structures are observed in the vicinity of the NADW/CDW front, and the associated temperature and salinity fluxes induced are strong, 5 x 10(-3)degrees cm/s and 2 x 10(-3) psu.m/s, respectively.