A DYNAMICALLY CONSISTENT ANALYSIS OF CIRCULATION AND TRANSPORTS IN THE SOUTHWESTERN WEDDELL SEA

An inverse model is applied for the analysis of hydrographic and curre nt meter data collected on the repeat WOCE section SR4 in the Weddell Sea in 1989-1992. The section crosses the Weddell Sea cyclonic gyre fr om Kapp Norvegia to the northern end of the Antarctic Peninsula. The c oncepts of geostrophy, conservation of planetary vorticity and hydrost atics are combined with advective balances of active and passive prope rties to provide a dynamically consistent circulation pattern. Our var iational assimilation scheme allows the calculation of three-dimension al velocities in the section plane. Current speeds are small except al ong the coasts where they reach up to 12 cm/s. We diagnose a gyre tran sport of 34 Sverdrup which is associated with a poleward heat transpor t of 28 x 10(12) W corresponding to an average heat Aux of 15 Wm(-2) i n the Weddell Sea south of the transect. This exceeds the estimated lo cal flux on the transect of 2 Wm(-2). As the transect is located mostl y in the open ocean, we conclude that the shelf areas contribute signi ficantly to the ocean-atmosphere exchange and are consequently key are as for the contribution of the Weddell Sea to global ocean ventilation . Conversion of water masses occuring south of the section transform 6 .6 +/- 1.1 Sv of the inflowing warm deep water into approximately equa l amounts of Weddell Sea deep water and Weddell Sea bottom water. The volume transport of surface water equals in the in- and outflow. This means that almost all newly formed surface water is involved in the de ep and bottom water formation. Comparison with the results obtained by pure velocity interpolation combined with a hydrographic data subset indicates major differences in the derived salt transports and the wat er mass conversion of the surface water. The differences can be explai ned by deviations in the structure of the upper ocean currents to whic h shelf areas contribute significantly. additionally a rigorous varian ce analysis is performed. When only hydrographic data are used for the inversion both the gyre transport and the poleward heat transport are substantially lower. They amount to less than 40% of our best estimat e while the standard deviations of both quantities are 6.5 Sv and 37 x 10(12) W, respectively. With the help of long-term current meter meas urements these errors can be reduced to 2 Sv and 8 x 10(12) W. Our res ult underlines the importance of velocity data or equivalent informati on that helps to estimate the absolute velocities.