The deep Scotia Sea is filled with ventilated Weddell Sea Deep Water (WSDW).This in turn is an essential contributor to the ventilation of theWorld Ocean abyss.Depending on the formation process and/or its location along the Weddell Seaperiphery, deep and bottom water masses follow different routes to crossthe South Scotia Ridge. A primitive equation, hydrostatic, ocean generalcirculation model (BRIOS1.1) with terrain-following coordinate is usedto investigate the water mass export from the Weddell Sea.The model is circumpolar focusing on the Weddell Sea, with particularlyhigh resolution (~ 20 km) in the DOVETAIL area.The northern limb of the Weddell Gyre exhibits an eastward Weddell Sea DeepWater transport across 44°W of 24 Sv.Export rates of Weddell Sea Deep Water through gaps in theSouth Scotia Ridge are estimated to be 6.4 Sv with asemi-annual cycle of ± 0.6 Sv, which can be correlated toatmospheric cyclone activity and Weddell Gyre strength.Sensitivity studies considering extreme sea ice conditions in the WeddellSea show higher (lower) exports in years of minimum (maximum) winter seaice extent. This can be attributed to the local change of the surfacestress achieved by wind and ice.Lagrangian particle trajectories, the so-called synthetic floats,illustrate the pathways of water masses from the inner Weddell Seainto the Scotia Sea through Orkney and Philip Passage, the major gapsin the South Scotia Ridge.They support the existing flow divergence known from observationson the northwestern continental shelf with one branch entering Bransfield Straitand the other continuingeastwards subsequently filling the deep Weddell and Scotia seas.The floats also highlight the interannual variability of the flow field.Water masses flowing through the major gaps originate from thesouthwestern and southeastern Weddell Sea continental shelves.However, water masses formed east of the Weddell Sea (e.g., Prydz Bay)also seem to feed the deep Scotia Sea, since a large portion of floatsflowing northward through the gaps of the South Scotia Ridge have beenin contact with the mixed layer processes outside the inner Weddell Sea.The propagation of dense water masses spreading from the southerncontinental shelf to the South Atlantic Ocean is estimated to be about8 years not including residence times on the continental shelf.
AWI Organizations > Climate Sciences > Climate Dynamics
AWI Organizations > Climate Sciences > Sea Ice Physics