Where Three Oceans Meet: The Agulhas Retroflection Region

• Main Author: Bennett, Sara L.
• Other Authors: WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
• Format: Text
• Language: English
• Published: 1988
• Subjects: Physical and Dynamic Oceanography; *OCEAN CURRENTS; RED SEA; OCEAN SURFACE; DYNAMICS; THEORY; WIND; PATHS; THESES; OPTICAL DATA; VORTICES; REFLECTION; OXYGEN; BOUNDARIES; TRANSPORT PROPERTIES; OCEANOGRAPHIC DATA; CURVATURE; INFRARED IMAGES; INTERNAL; LINEARITY; ARTIFICIAL SATELLITES; FLUIDS; FILAMENTS; OCEANS; BAROMETRIC PRESSURE; RINGS; SALINITY; AIR WATER INTERACTIONS; SURFACE TEMPERATURE; STRATIFICATION; SEA WATER; DEEP WATER; HYDROGRAPHIC SURVEYING; SUBSURFACE; THERMOCLINES; FRONTS(OCEANOGRAPHY); GRADIENTS; INDIAN OCEAN; RECIRCULATION; SOUTH ATLANTIC OCEAN; LOW TEMPERATURE; STABILITY; AGULHAS CURRENTS; SOUTHERN OCEAN; RETROREFLECTION(OCEAN CURRENTS); WESTERN BOUNDARY CURRENTS; Indian; Southern Ocean; South Atlantic Ocean
• Online Access: http://www.dtic.mil/docs/citations/ADA204684; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA204684

The Agulhas Retroflection south of Africa lies at the junction of the S. Indian, S. Atlantic, and Circumpolar Oceans. A March 1985 survey, including hydrographic stations, subsurface current path survey, and contemporaneous sea surface temperature (SST) satellite infrared image, plus historical data, are used to characterize the region. In 1985, Agulhas transport was 56 to 95 Sv (1 million m/s; relative to 2400 dbar), up to 1.5 times the interior transport from linear theory and observed winds. Return Current transport was 54 and 65 Sv. The current retroflected in two branches. The surface warm core retroflected upstream of the second branch, while an SST front, and the subsurface current path survey, followed it. A cold ring, with 64 Sv transport but no SST anomaly, and a ware recirculation lay between the branches. Curvature vorticity at anticyclonic turns in the path exceeded the gradient wind maximum, so other dynamics must locally contribute. Salt, oxygen, and potential vorticity fronts on isopycnals in the current's upper approx. 300 m are observed, as are deep western boundary filaments of Red Sea Water and N. Atlantic Deep Water influences. The current meets baroclinic barotropic instability necessary conditions. Thermocline water (>8C) transport into the S. Atlantic is 2.8 to <9. 6 Sv, less than the > or = 10 Sv Atlantic export of deep water. Keywords: Agulhas currents, Oceanographic data; Optical data; Air water interactions; Western boundary current; Oceanographic fronts; Salinity; Ocean currents; Indian Ocean; South Atlantic Ocean. Theses. Prepared in cooperation with Massachusetts Inst. of Tech., Cambridge. Sponsored in part by Contract N00014-87-K-0007.