ARTICLES The response of the Antarctic Circumpolar

• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2008
• Subjects: Antarctic; Southern Ocean; The Antarctic; Antarc*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.419.8633; http://www.seas.harvard.edu/climate/seminars/pdfs/boning2008.pdf

Observations show a significant intensification of the Southern Hemisphere westerlies, the prevailing winds between the latitudes of 30 ◦ and 60 ◦ S, over the past decades. A continuation of this intensification trend is projected by climate scenarios for the twenty-first century. The response of the Antarctic Circumpolar Current and the carbon sink in the Southern Ocean to changes in wind stress and surface buoyancy fluxes is under debate. Here we analyse the Argo network of profiling floats and historical oceanographic data to detect coherent hemispheric-scale warming and freshening trends that extend to depths of more than 1,000 m. The warming and freshening is partly related to changes in the properties of the water masses that make up the Antarctic Circumpolar Current, which are consistent with the anthropogenic changes in heat and freshwater fluxes suggested by climate models. However, we detect no increase in the tilt of the surfaces of equal density across the Antarctic Circumpolar Current, in contrast to coarse-resolution model studies. Our results imply that the transport in the Antarctic Circumpolar Current and meridional overturning in the Southern Ocean are insensitive to decadal changes in wind stress. The Antarctic Circumpolar Current (ACC) is the dominant feature of ocean circulation in the Southern Hemisphere 1. Driven at least in part by the vigorous mid-latitude westerly winds, the ACC is associated with strongly tilted surfaces of constant density in the meridional direction. As these provide an effective