Datensatz

Zusammenfassung

Significant centennial-scale oscillations have been observed in key features of the Southern Ocean within the CMIP6 ensemble. In several members of the ensemble these oscillations can be explained via a novel mode of deep ocean heat redistribution. This mode of variability leads to significant changes in the Antarctic Circumpolar Current and motion of subsurface heat, with changes in the Antarctic Circumpolar Current of up to 15Sv or roughly 10-15% of the current strength. This significant magnitude and period of roughly 100 years means that the mode could have a sizeable confounding impact on our future climate change predictions. The dynamical behaviour of this mode was analysed across an ensemble of models, with the CanESM5 model being chosen as an exemplar case study. The mode and associated centennial oscillations more broadly were characterised to understand the key dynamical factors and the regions of interest. The heat mode is found to be associated with variability in the lower overturning cell, and involve a redistribution of deep ocean heat between the ACC and subpolar regions, with two broad longitudinal 'cells' identified. Detailed heat and Walin budgets as well as lagged correlation analysis was undertaken to establish the potential drivers and dynamics for this mode and investigate links with processes such as deep convection around the Antarctic.