ON THE SUBTROPICAL CONVERGENCE IN THE SOUTH-ATLANTIC OCEAN

The surface expression of the Subtropical Convergence has been considered to form a major boundary between Subtropical Surface Water of the subtropical gyres of the Southern Hemisphere and Subantarctic Surface Water of the Southern Ocean to the south. One of the ocean areas for which least is known about this front is the mid-South Atlantic. We present here results of an analysis of a few available data sets pertaining to this front, particularly in the vicinity of the Tristan da Cunha island group. It is shown that, although the meridional range of the Subtropical Convergence over-lies these islands, there is no unambiguous evidence that its north-south movement has a clear seasonal cycle. The surface expression of the Subtropical Convergence in the mid-South Atlantic may be intermittent and ephemeral, rather than weak, and may be more strongly evident as a salinity front than as a thermal front.