Stochastically forced variability in the Antarctic Circumpolar Current

Interannual fluctuations in the Antarctic Circumpolar Current (ACC) were considered. In the present study we analyze a mode of variability in the Hamburg Large-Scale Geostrophic ocean general circulation model which was driven by stochastic atmospheric forcing. The short-term atmospheric weather fluctuations were represented by a number of spatially coherent patterns of momentum, heat, and freshwater flux which were superimposed onto the climatological fluxes. These patterns were derived from an experiment with an atmospheric general circulation model forced with observed sea surface temperatures, and they were chosen randomly at each month. We found anomalies which propagate along the ACC at an interannual timescale. They can be explained by the combined effects of anomaly advection with the mean ocean circulation and integration of the short-term atmospheric weather fluctuations. Some similarities were found between our results and the concept of the Antarctic Circumpolar Wave, which was proposed recently to account for large-scale anomalies which propagate along the ACC in both the atmosphere and the ocean.