Decadal SST Variability in the Southern Ocean in CMIP Simulations

The characteristics and causes of interannual-decadal sea surface temperature (SST) variability in the Southern Ocean are investigated within the simulations of the Climate Model Intercomparison Project Phase 3 and 5 (CMIP3 and CMIP5) data base and in idealized forced ocean general circulation model simulations. We will compare the leading modes of SST variability against several simple null hypotheses, such as isotropic diffusion (red noise) and a Slab Ocean model, to investigate the sources of decadal variability. In this we will show that characteristic multi-decadal variability patterns exist in the Southern Ocean that are beyond a simple red noise. The results show that the atmospheric forcing not only affects the SST modes on shorter time-scales directly, but also show its influence on longer time scales via air-sea interaction and oceanic feedback. The deep mixed layer in the Southern Ocean is an essential element to maintain the long-term SST variability while the ocean dynamics connect the entire ocean and create the homogeneous-like spatial patterns via advection effect.