Benguela Sources and Transport (BEST)
June 1992 and November 1993

Description

Wind-driven ocean circulation models, as well as field observations reveal significant transfer of Indian Ocean Central (thermocline) Water into the South Atlantic Ocean. The transfer is accomplished by an eddy shedding process at the western end of the Agulhas Retroflection and by intermittent streams or plumes of Indian Ocean water injected into the Benguela Current. The heat content, salt content and rotational energy of the transferred water influence the state of the Atlantic Ocean. Perhaps the most profound effect is that the Atlantic's salinity is increased by drawing salty water from the evaporative Indian Ocean. A saltier Atlantic may be linked with increased formation of North Atlantic Deep Water and the associated vigor of the global thermohaline circulation. The thermohaline circulation is an integral part of the global climate system.

The transport of the Benguela Current and its variability is measured by a moored array of instruments as well as analysis of the TOPEX/POSEIDON satellite altimeter and CTD density field observations. The source of the water is determined by analysis of the water mass properties measured from CTD observations.

To accomplish the BEST objectives, an extensive field program was carried out between June 1992 and November 1993. The field work consisted of three hydrographic surveys and a moored array of inverted echo sounders (IES), inverted echo sounders with pressure gauges (PIES) and current meter moorings (CMM). The BEST mooring array was deployed in June 1992 and, during October/November 1993, 4 PIES and 4 current meter moorings (CMM) along 30S, and 2 IES at the edges of the line Cape Town 37.5S ,12.3E were recovered. The location of the moorings as well as the CTD and XBT stations obtained during the three BEST cruises are shown in Figure 1.
A more detailed description is given in an article in WOCE Notes Vol. 6 by S. Garzoli, A. Gordon and D. Pillsbury.

Designed by: D. Jarvis Belinne
Lamont-Doherty Earth Observatory of Columbia University