Surface oceanic fronts between Africa and Antarctica

Abstract

A study of the location of oceanic fronts during austral summers 1993–1995 in the Southern Ocean south and east of South Africa was carried out. Continuously sampled surface temperature and salinity data enable the locations and structures of oceanic fronts to be examined in greater detail than do discrete measurements. Nine fronts, including those of the Antarctic Circumpolar Current (ACC), are identified and their average positions and characteristic temperatures and salinities from 61 crossings during 19 legs of four UK WOCE (World Ocean Circulation Experiment) cruises are presented and discussed. The Agulhas Return Front is identified in surface water as far east as 56°E. The South Subtropical Front is distinguished from the North Subtropical Front, and its characteristic stepped structure with small bands of homogeneous water between steps is described. Two separate surface features associated with the Polar Front are identified northwest and southeast of Kerguelen. Surface manifestations of the southern ACC front and southern boundary of the ACC are located south of the Kerguelen Plateau. It is suggested that the so-called “Crozet Front”, where several fronts apparently merge, is a result of widely spaced sampling, and such features can be resolved into the individual fronts with continuous surface sampling. The fine scale features common in this region are discussed, including temperature inversions south of fronts and the presence of meanders and cyclonic and anticyclonic eddies.