Intermediate water in the Brazil-Malvinas Confluence Zone: A Lagrangian view

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Boebel, Olaf, Schmid, Claudia, Podesta, Guillermo, Zenk, Walter
• Format: Article in Journal/Newspaper
• Language: English
• Published: AGU (American Geophysical Union) 1999
• Subjects: Antarctic; Antarc*
• Online Access: https://oceanrep.geomar.de/id/eprint/685/; https://oceanrep.geomar.de/id/eprint/685/1/1999JC900059.pdf; https://doi.org/10.1029/1999JC900059

The subsurface flow within the subantarctic and subtropical regions around the Brazil-Malvinas (Falkland) Confluence Zone is studied, using daily hydrographic and kinematic data from four subsurface floats and a hydrographic section parallel to the South American shelf. The float trajectories are mapped against sea surface flow patterns as visible in concurrent satellite sea surface temperature (SST) images, with focus on the November 1994 and October/November 1995 periods. The unprecedented employment of Lagrangian θ-S diagrams enables us to trace the advection of patches of fresh Antarctic Intermediate Water (AAIW) from the Confluence Zone into the subtropical region. The fresh AAIW consists of a mixture of subtropical AAIW and Malvinas Current core water. Within the subtropical gyre, these patches are discernible for extended periods and drift over long distances, reaching north to 34°S and east to 40°W. The cross-frontal migration of quasi-isobaric floats across the Confluence Zone from the subtropical to the subantarctic environment is observed on three occasions. The reverse process, float migration from a subpolar to a subtropical environment was observed once. These events were located near 40°S, 50°W, the site of a reoccurring cold core feature. Subsurface float and SST data comparison reveals similarities with analogous observations made in the Gulf Stream [Rossby, 1996] where cross-frontal processes were observed close to meander crests. The limited number of floats of this study and the complex structure of the Brazil-Malvinas Confluence Zone, however, restricts the analysis to a description of two events.