Kinematic elements of Antarctic Intermediate Water in the western South Atlantic

• Main Authors: Olaf Boebel, Claudia Schmid, Walter Zenk
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1998
• Subjects: Antarctic; Argentine; Antarc*; North Atlantic Deep Water; North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.454.6190; http://www.aoml.noaa.gov/phod/docs/boebel_et_al1999a.pdf

The northward ßowing Antarctic Intermediate Water (AAIW) is a major contributor to the large-scale meridional circulation of water masses in the Atlantic. Together with bottom and thermocline water, AAIW replaces North Atlantic Deep Water that penetrates into the South Atlantic from the North. On the northbound propagation of AAIW from its formation area in the south-western region of the Argentine Basin, the AAIW progresses through a complex spreading pattern at the base of the main thermocline. This paper presents trajectories of 75 subsurface ßoats, seeded at AAIW depth. The ßoats were acoustically tracked, covering a period from December 1992 to October 1996. Discussions of selected trajectories focus on mesoscale kinematic elements that contribute to the spreading of AAIW. In the equatorial region, intermittent westward and eastward currents were observed, suggesting a seasonal cycle of the AAIW ßow direction. At tropical latitudes, just o⁄shore the intermediate western boundary current, the southward advection of an anticyclonic eddy was observed between 5¡S and 11¡S. Farther o⁄shore, the ßow lacks an advective pattern and is governed by eddy di⁄usion. The westward subtropical gyre return current at about 28¡S shows considerable stability, with the mean kinetic energy to eddy kinetic energy ratio being around one. Farther south, the eastward deeper South Atlantic Current is dominated by large-scale meanders with particle velocities in excess of 60 cm s~1. At the Brazil—Falkland Current Conßuence Zone, a cyclonic eddy near 40¡S 50¡W seems to act as injector of freshly mixed AAIW into the subtropical gyre. In general, much of the mixing of the various blends of AAIW is due to the activity of mesoscale eddies, which frequently reoccupy similar positions. ( 1999 Elsevier