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An inverse model is applied for the analysisof hydrographic and current meter data collected on the repeat WOCE section SR4in the Weddell Sea in 1989–1992. The section crosses the Weddell Sea cyclonicgyre from Kapp Norvegia to the northern end of the Antarctic Peninsula. Theconcepts of geostrophy, conservation of planetary vorticity and hydrostatics arecombined with advective balances of active and passive properties to provide adynamically consistent circulation pattern. Our variational assimilation schemeallows the calculation of three-dimensional velocities in the section plane.Current speeds are small except along the coasts where they reach up to 12 cm/s.We diagnose a gyre transport of 34 Sverdrup which is associated with a polewardheat transport of 28×1012 W corresponding to an average heat flux of15 Wm–2 in the Weddell Sea south of the transect. This exceeds theestimated local flux on the transect of 2 Wm–2. As the transect islocated mostly in the open ocean, we conclude that the shelf areas contributesignificantly to the ocean-atmosphere exchange and are consequently key areasfor the contribution of the Weddell Sea to global ocean ventilation. Conversionof water masses occuring south of the section transform 6.6±1.1 Sv of theinflowing warm deep water into approximately equal amounts of Weddell Sea deepwater and Weddell Sea bottom water. The volume transport of surface water equalsin the in- and outflow. This means that almost all newly formed surface water isinvolved in the deep and bottom water formation. Comparison with the resultsobtained by pure velocity interpolation combined with a hydrographic data subsetindicates major differences in the derived salt transports and the water massconversion of the surface water. The differences can be explained by deviationsin the structure of the upper ocean currents to which shelf areas contributesignificantly. Additionally a rigorous variance analysis is performed. When onlyhydrographic data are used for the inversion both the gyre transport and thepoleward heat transport are substantially lower. They amount to less than 40% ofour best estimate while the standard deviations of both quantities are 6.5 Svand 37×1012 W, respectively. With the help of long-term currentmeter measurements these errors can be reduced to 2 Sv and 8×1012 W.Our result underlines the importance of velocity data or equivalent informationthat helps to estimate the absolute velocities. Key words. Oceanography: General (Arctic and antarcticoceanography) · Oceanography: Physical (General circulation; Hydrography)</p

A dynamically consistent analysis of circulation and transports in the southwestern Weddell Sea