To investigate regional and interannual variability of the ecosystem in the Southern Ocean, a coupled circumpolar ice-ocean-plankton model has been developed.The ice-ocean component (known as BRIOS-2) is based on a modified version of the s-Coordinate Primitive Equation Model (SPEM) coupled to a dynamic-thermodynamic sea ice-model.The biological model (BIMAP) comprises two biogeochemical cycles - silica and nitrogen - and a prognostic iron compartment to include possible effects of micronutrient limitation.Simulations with the coupled ice-ocean-plankton model indicate that the physical-biological interaction is not limited to the effect of a varying surface mixed layer depth.In the Pacific sector, large anomalies in winter mixed layer depth cause an increased iron supply and enhanced primary production and plankton biomass in the following summer, whereas in the Atlantic sector variability in primary production is caused mainly by fluctuations of oceanic upwelling.Thus, the ACW induces regional oscillations of phytoplankton biomass in both sectors, but not a propagating signal.Furthermore, interannual variability in plankton biomass and primary production is strong in the Coastal and Continental Shelf Zone and the Seasonal Ice Zone around the Antarctic continent.Interannual variability induced by the ACW has large effects on the regional scale, but the associated variability in vertical carbon fluxes is negligible compared to the long-term carbon sequestration of the Southern Ocean.keywords: ACW, Southern Ocean, plankton biomass, primary production, interannual variability