On the multi-century Southern Hemisphere response to changes in atmospheric CO2-concentration in a Global Climate Model

• Main Authors: Meteorol Atmos Phys, M. L. Bates, M. H. Engl, W. P. Sijp
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2004
• Subjects: Antarctic; Southern Ocean; The Antarctic; Weddell Sea; Ross Sea; Pacific; Weddell; Antarc*; Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.684.8556; http://web.science.unsw.edu.au/%7Ematthew/bes_2005.pdf

climate change is examined using an intermediate complex-ity climate model. Unlike previous studies, the Southern Ocean response on the centennial to multi-centennial time-scale is assessed in some detail. It is shown that changes in atmospheric CO2-concentrations lead to an increase in the strength of the Antarctic Circumpolar Current (ACC) by 20 Sv by 2750 for an atmospheric CO2-concentration of 750 ppm. This increase is predominantly the result of an enhanced steric height gradient. The increase in the strength of the ACC induces changes in its steering around topo-graphic features. This change in ACC pathway causes increased surface flow of colder waters into some regions (reducing the rate of warming) and increased surface flow of warmer waters into others (increasing the rate of warm-ing). This meridional shifting of the ACC causes changes in atmospheric temperature in the Southern Hemisphere to be nonuniform. It is also shown that the strength and location of the Antarctic Bottom Water (AABW) overturning cell is affected by increased atmospheric CO2. For a CO2-concen-tration scenario increasing gradually to 750 ppm, AABW production initially decreases, then recovers and eventually increases. New production zones form, which extend AABW production all the way from the Weddell Sea east-ward into the Ross Sea. These new production zones are the result of increased areas of atmosphere-ocean interactions, due to decreased sea-ice coverage, although the overturned waters are now warmer and fresher due to climate change. A new production zone of Antarctic Intermediate water is also established in the Southeast Pacific Ocean, poleward of its present-day location. 1.