Ventilation and carbon uptake in the southern oceans: Response to wind stress changes

Darryn Waugh, Johns Hopkins University, Department of Earth and Planetary Sciences, Baltimore, United States, Thomas W N Haine, Johns Hopkins Univ, Baltimore, MD, United States, Matthew H England, Univ New South Wales, Sydney, Australia, Paul Spence, University of New South Wales, Climate Change Research Centre, Sydney, NSW, Australia and Andrew M Hogg, Australian National University, Research School of Earth Sciences, Canberra, ACT, Australia
Changes in the ventilation and uptake of anthropogenic carbon (Cant) in southern mode and intermediate waters to changes in the overlying westerly winds is examined by analyzing simulations with abrupt increase and/or shift in the winds. It is shown that a barotropic response, following Sverdrup balance, can explain much of the response of the ideal age (mean ventilation time) and Cant. In contrast, these responses cannot be explained by changes in subduction rates or the MOC. For an increase in the winds there is an intensification of the gyres and a decrease in age and increase in Cant throughout intermediate/mode waters. In contrast, age decreases (Cant increases) only south of 35S for a poleward shift in the winds, with the opposite sign changes north of this latitude. As a consequence, there is an increase in the volume of young waters and Cant in mode/intermediate waters for an increase in the winds but only a small net change in both quantities for a shift in the winds.