HR: 11:05h
AN: PP22A-04    [Abstracts]
TI: Is there a bi-Polar Ocean Seesaw?
AU: * Stouffer, R J
EM: ronald.stouffer@noaa.gov
AF: Geophysical Fluid Dynamics Laboratory, Route 1, Princeton, NJ 08542
AU: Seidov, D
EM: dseidov@essc.psu.edu
AF: The Pennsylvania State University, 2217 Earth & Engineering Science Bldg, University Park, PA 16802
AB: In ice records from Antarctica and Greenland, it has been noted that when one hemisphere is warm, the other hemisphere is cold and vice versa. Some paleodata and ocean-only modeling imply that this may be because the ocean thermohaline circulation (THC) behaves as a seesaw swinging from a regime with weaker North Atlantic Deep Water (NADW) formation to a regime with stronger NADW formation. These northern hemisphere regimes are associated with stronger and weaker Antarctic Deep Water formation, respectively. The seesaw supposedly can be driven by change of freshwater flux either in the northern North Atlantic or in the Southern Ocean. Here we investigate this issue using a fully coupled advanced ocean-atmosphere-land surface-sea ice model . The Manabe Climate Model (MCM) is used in idealized scenarios that we believe are favorable to alleged bi-polar seesaw regimes. The GFDL R30 atmosphere-ocean model is forced with a freshwater flux anomaly of 1 SV persisting for 100 model years beginning from a control integration. After 100 years, this additional freshwater flux is turned off and the model climate is allowed to recover. In one integration, the additional freshwater is added in the high latitudes of the North Atlantic Ocean. In the second integration, the excess of freshwater is added in the high latitudes of the Southern Ocean. In both cases, oceanic convection and the associated THC local to the freshwater input is greatly hindered and slowed down. This results in a large local cooling and freshening of the surface waters. The hemisphere with the freshwater input tends to cool at the surface, while the opposite hemisphere tends to warm. This supports the seesaw hypothesis. However, the response of most the climate system is much more complicated, and the simplistic seesaw concept needs to be reconsidered. These features will be discussed.
DE: 4215 Climate and interannual variability (3309)
DE: 4267 Paleoceanography
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting