Sub-Antarctic Flux and Dynamics Experiment (SAFDE): Overview with Some Descriptive Results

Douglas S. Luther, Univ. of Hawaii at Manoa, Honolulu, Hawaii
D. Randolph Watts, Univ. of Rhode Island, Kingston, Rhode Island
Alan D. Chave, Woods Hole Oceanographic Institution, Woods Hole, Mass.
James G. Richman, Oregon State Univ., Corvallis, Oregon
Stephen R. Rintoul, CSIRO Marine Laboratories, Hobart, Australia
John A. Church, CSIRO Marine Laboratories, Hobart, Australia
Jean H. Filloux, Scripps Institution of Oceanography, La Jolla, California


Summaries of the structure and variability of the absolute (barotropic and baroclinic) currents associated with the Sub-Antarctic Front (SAF) southwest of Tasmania (along SR3) will be presented, using data from a large array of instruments deployed from 3/'95 to 3/'97. The broad intent of SAFDE was to obtain long-duration, spatially coherent measurements of current and temperature (which has been achieved and will be exhibited) in order to provide information on property fluxes and dynamic balances, and their variations relative to the location of the SAF and with respect to time. The suite of instruments deployed incorporates both well-established ideas of oceanographic experimentation, as well as novel approaches. The former is represented by a seven-element current meter mooring array, where each sub-surface mooring supports 1-5 current meters and up to 2 additional temperature sensors from 300 m to as deep as 3200 m. Straddling this LDA, and extending approximately 450 km along a NNE-SSW line, is an array of 12 horizontal electrometers (HEMs) and 18 inverted echo sounders (IESs). These seafloor instruments are well suited for observing currents at mid- to high latitudes where large vertical scales dominate. The HEMs alone provide direct measurements of the horizontal transport (barotropic) components. The IESs and HEMs combined will provide, at least, both horizontal components of a barotropic and (empirical) gravest baroclinic mode description of the horizontal current field. The less conventional HEM/IES data will be emphasized in this presentation, with additional information being provided by altimetry and by several hydrographic cruises (two with differential GPS-referenced shipboard ADCPs). The coherence and structural differences between barotropic and baroclinic components will be emphasized.