Topic: The role of the Southern Ocean in overturning pathways and transients
Abstract: Climate variability occurs over a range of time scales, from the large seasonal cycle in Antarctic sea ice extent to the reorganization of the overturning circulation across glacial-interglacial cycles. Using a time-dependent, idealized model of global water mass transformation, transitions in the three dimensional structure of the global overturning circulation, including both meridional and zonal components, will be explored with emphasis on constraints imposed by surface buoyancy forcing in the Southern Ocean. A major focus will be the presentation of a mechanistic explanation for Dansgaard-Oeschger (DO) events. DO events are periods of abrupt climate variability during the last glacial period characterized by cooling in Antarctica during warm periods in Greenland and vice versa. Coupled changes to both the low-latitude stratification and reorganization of the surface buoyancy distribution in the Southern Ocean, in response to rapid changes in North Atlantic Deep Water formation, are consistent with both a bi-polar seesaw behavior and the Southern Hemisphere's observed 200-yr lag. Evidence of these dynamics in more realistic circulation models will be discussed.
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