Representation of Southern Ocean circulation variability in a global finite-element coupled sea ice--ocean model

Ralph.Timmermann [ at ]


The Finite-Element coupled Sea ice--Ocean Model (FESOM) has been developed at the Alfred Wegener Institute for Polar and Marine Research.Its sea-ice component is a dynamic-thermodynamic model with an elastic-viscous-plastic rheology.The ocean component is the primitive-equation Finite Element Ocean Model (FEOM).An eight-compartment model of the marine ecosystem, featuring nitrate and silicate cycles and considering possible iron limitation, has been implemented.The coupled model has been configured on a global grid with $1.5^\circ$ mean resolution.Vertical coordinate follows a z-level approach and uses a tetrahedral discretization.Shaved cells at the bottom ensure a continous (not step-wise) representation of topography with correct depths.Multi-decadal simulations have been performed using atmospheric forcing data from the NCEP reanalysis. Results are analysed with regard to ice concentration and thickness, as well as ocean hydrography and circulation.The model features a largely realistic representation of sea-ice coverage and large-scale ocean circulation.Weddell Sea water mass characteristics and formation pathways are quite realistic.Salinity of High Salinity Shelf Water exceeds 35 psu and therefore appears to be overestimated; this however enables the model HSSW to trigger the formation of Weddell Sea Deep and Bottom Water despite the model's relatively coarse resolution.Simulated mean ACC transport at Drake Passage is about 130 Sv; its variability is strongly correlated with bottom pressure gradients and reflects the Southern Annular Mode.Small but significant out-of-phase variations of the ACC transports at different sections imply a fluctuating redistribution of water mass between the Atlantic, Indic, and Pacific Oceans.

Item Type
Conference (Poster)
Publication Status
Event Details
Polar Dynamics Conference, Bergen, Norway, August 29-31.
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Cite as
Timmermann, R. , Böning, C. , Danilov, S. and Schröter, J. (2007): Representation of Southern Ocean circulation variability in a global finite-element coupled sea ice--ocean model , Polar Dynamics Conference, Bergen, Norway, August 29-31 .

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