HR: 0800h
AN: OS41A-0592    [Abstracts]
TI: Role of the Freshwater Forcing on the Atlantic Thermohaline Circulation in Climate Changes
AU: * Murakami, S
EM: smurakam@jamstec.go.jp
AF: Frontier Research Center for Global Change, Japan Agency for Marine-Earth Science and Technology, Showamachi 3173-25, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Kitoh, A
EM: kitoh@mri-jma.go.jp
AF: Meteorological Research Institute, Nagamine 1-1, Tsukuba, 305-0052 Japan
AB: Effects of the freshwater forcing changes on the thermohaline circulation (THC) differ depending on as to which regimes the circulation is in. This fact is obvious from the considerations based on the simple conceptual box models like Stommel 1961 or Rahmstorf 1996. However, the THC regime of the real Atlantic is not obvious including the problem as to whether such a simple view is applicable or not. In this study, the authors try to determine the Atlantic THC regime of the MRI-CGCM2 from an analysis of a partially coupled experiment, where the greenhouse gas concentrations are fixed to the present-day values but the ocean surface freshwater flux is taken from a transient global warming experiment. Such an experiment is thought to show the role of freshwater forcing more clearly then a fully coupled transient global warming simulation. Analyses show that the salt content of the northern North Atlantic increases in the case of global warming as a long-term response although the water flux over there makes the surface water fresher. It stabilize (or enhance) the Atlantic THC as a long-term response. This response of the THC to an increased freshwater forcing suggests that the THC of the MRI-CGCM2 is in the thermohaline driven regime in the context of the boxmodels. The freshwater flux adjustment used in the MRI-CGCM2 make the problem somewhat complicated. However, a consideration based on the box model and the Atlantic freshwater budget suggests that this result can be generalized to other AOGCMs and/or the real world.
DE: 1620 Climate dynamics (0429, 3309)
DE: 1635 Oceans (1616, 3305, 4215, 4513)
DE: 4962 Thermohaline
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005