Ozone depletion leading force for Southern Ocean change

Abstract

Previous studies have suggested that key aspects of the Southern Ocean are affected by elevated atmospheric carbon dioxide levels. Increasing greenhouse gas (GHG) concentrations, which strengthen surface winds over much of the Southern Ocean, may increase flow rates in the Antarctic Circumpolar Current (ACC), induce a temperature disparity between the northern and central Southern Ocean, and affect the strength of the meridional ocean circulation (MOC). But GHGs are not the only set of compounds arising from human activity that can trigger these changes. Stratospheric ozone depletion due to such ozone‐depleting substances (ODSs) as chlorofluorocarbons, whose production and use were heavily regulated by the 1987 Montreal Protocol, results in similar changes. Using an atmosphere‐ocean coupled general circulation model that allows for detailed calculations of stratospheric chemistry, Sigmond et al. simulated past and future changes for the Southern Ocean due to both GHGs and ODSs. Their model calculations suggest that ODSs, which peaked in concentration in 1995, will be the dominant driver of changes in ACC until the second quarter of the 21st century, at which point the monotonically increasing GHG levels will take over. Further, they found that the peak impact of ODSs on ACC will occur a few decades after their peak concentration. The authors suggest that future research needs to take into account the effects of ozone depletion—something not ordinarily done in investigations of Southern Ocean behavior. (Geophysical Research Letters, doi:10.1029/2011GL047120, 2011)