Interbasin Differences in Ocean Ventilation in Response to Variations in the Southern Annular Mode

The response of the ventilation of mode and intermediate waters to abrupt changes in the Southern Annular Mode (SAM) is examined by analyzing the ideal age in a global ocean-sea ice model. The age response is shown to differ between the central Pacific Ocean and other basins. In the central Pacific there are large decreases in the age of subtropical mode and intermediate waters associated with a more positive SAM, contrasting only small age changes in the Atlantic and Indian Oceans, except near where intermediate water density surfaces outcrop. These interbasin differences hold for simulations at different horizontal resolutions, and can be explained by the zonal variations in wind stress changes associated with the SAM. These results suggest that the carbon and heat uptake associated with the SAM will likely vary between ocean basins.