Synoptic Structure of the Sub-Antarctic Front Southwest of Tasmania: Temperature, Salinity and Absolute Velocity

Christopher S. Meinen, Univ. of Hawaii at Manoa, Honolulu, Hawaii
Douglas S. Luther, Univ. of Hawaii at Manoa, Honolulu, Hawaii


The mean ``synoptic" structure of the northern, strongest, branch of the Antarctic Circumpolar Current southwest of Tasmania - the Sub-Antarctic Front (SAF) - is estimated by a stream-coordinates analysis of data from overlapping arrays of current meter moorings, inverted echo sounders, and horizontal electric field recorders deployed during the 1995-97 Sub-Antarctic Flux and Dynamics Experiment ( An accurate stream coordinates reference frame is constructed without the usual suppositions about the behavior of the structure of the density or current fields (e.g. a frozen field assumption). The stream coordinates are derived from a daily objective mapping of the temperature field obtained from combining the IES travel time measurements with an empirical vertical mode structure constructed from the extensive hydrography acquired during WOCE (SR3 line). Full-water-column stream-coordinates sections of temperature, salinity and absolute velocity will be discussed and compared with prior observations of the SAF and other fronts. Separating the baroclinic and barotropic currents (using the Fofonoff bottom current definition of barotropic) reveals that (i) the SAF currents are divergent - both baroclinically and barotropically - in the cross-stream direction, and (ii) the cross-stream shear of the along-stream velocity is strongest on the cold side of the front. The barotropic contribution to the mean total transport is small. Dynamical inferences will be drawn from the stream coordinates sections.