David Marshall

Abstract:

We use a sector con guration of an ocean general circulation model to examine the sensitivity of circumpolar transport and meridional overturning to changes in Southern Ocean wind stress and global diapycnal mixing. We nd that at eddy-permitting, and ner, resolution the sensitivity of circumpolar transport to forcing magnitude is drastically reduced. At su ciently high resolution, there is little or no sensitivity to wind stress, even in the limit of no wind. In contrast, the meridional overturning circulation continues to vary with Southern Ocean wind stress, but with reduced sensitivity in the limit of high wind stress. We nd that both the circumpolar transport and meridional overturning continue to vary with diapycnal di usivity at all model resolutions. The circumpolar transport becomes less sensitive to changes in diapycnal di usivity at higher resolution, although sensitivity always remains. In contrast, the overturning circulation is more sensitive to change in diapycnal di usivity when the resolution is high enough to permit mesoscale eddies. These models cast doubt upon the validity of climate projections obtained using non-eddy-resolving ocean models.