Wassermassentransformation im Weddell-Wirbel: Tracerstudien mit dem hydrostatischen, regionalen Ozeanmodell BRIOS

Abstract

The water mass transformation and the associated Deep/Bottom Water (DBW) formation are analyzed with a regional ocean circulation model of theSouthern Ocean. Simulated CFC concentrations and saturation of the mixed layer are in good agreement with observations. Sea ice,temperature and salinity and their fluxes influence the flux of tracers. High fluxes of salinity and temperature perturb the stability of the water column, initiates convection and entrain tracer poor water into the mixed layer. High Fluxes are essential for the DBW formation. DBW is primarily formed in the WeddellSea, in front of the Ross Ice Shelf (ROSS) and Amery Ice Shelf (AMERY) and spread with the boundary currents: the boundary current from ROSS develops two branches: one ventilates the Ross Gyre and the other Antarctic Coastal Current; AMERY ventilates the Antarctic Coastal Current; DBW formed in front of the Filchner Ronne Ice Shelf (FRIS) flows along the Antarctic Peninsula and partly leaves the Weddell Sea. Cross sections shows that the model doesn´t reproduce CFC cores. However, at the continental slope in the depth of the core the simulated concentrations correspond to the observed concentrations. The discrepancy can be traced back to input of simulated containing CFC water masses at ocean depths between 150-1200m instead to the abyssal ocean.:p:The DBW formation rates of the Southern Ocean were determined by tracer budget calculations. The DBW formation rates of the SouthernOcean average 5-15Sv according to water masses. However, the formation rates for a given water mass and constant overturning depend on the chosen tracer and time observation.:p:The explicitly formulated interaction between ocean and ice shelf is used to describe the input of He and Ne. The good agreement between Simulation and Observation values confirms the approach. Increase of measurement accuracy to ±0.2% would improve the detection of Ice Shelf Water from ROSS and AMERY.