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 combination of zonal
variations in wind stress changes associated with the SAM, and
differences in the age response to an increase or shift in the wind
stress. These results suggest that the carbon and heat uptake associated
with the SAM will likely vary between ocean basins.