HR: 11:20h
AN: PP22A-05    [Abstracts]
TI: The Transient Atmosphere-Ocean Response to Fresh Water Perturbations Applied to the North Atlantic Basin
AU: * Vettoretti, G
EM: guido@atmosp.physics.utoronto.ca
AF: Department of Physics, University of Toronto, 60 St. George Street, Toronto, ON M5S 1A7 Canada
AU: Stastna, M
EM: mmstastna@math.uwaterloo.ca
AF: Department of Applied Mathematics, University of Waterloo, 200 University Ave. West, Waterloo, ON N2L 3G1 Canada
AU: Peltier, W R
EM: peltier@atmosp.physics.utoronto.ca
AF: Department of Physics, University of Toronto, 60 St. George Street, Toronto, ON M5S 1A7 Canada
AB: The issue of climate system instability involving rapid changes in the thermohaline circulation (THC) of the Atlantic Ocean is a continuing focus of climate dynamics research. As a contribution to the WCRP/CLIVAR coupled model and paleoclimate model inter-comparison projects (CMIP/PMIP), a series of experiments have been performed in which a range of different fresh water forcing anomalies have been applied to the North Atlantic Basin between 50 and 70 degrees north latitude. In the first experiment an equilibrated modern pre-industrial simulation, constructed using the NCAR CCSM, version 1.4, is forced with a fresh water forcing (FWF) anomaly of 0.1 Sv for 100 years and subsequently allowed to recover. A second experiment is also performed in which the 100 year FWF anomaly is increased to 1 Sv and the climate once more allowed to fully recover after this forcing is removed. This paper will describe the transient evolution of the global climate system before, during, and after the FWF anomaly is applied. Of particular interest is the large difference in response between the 0.1 Sv and 1 Sv experiments. The 0.1 Sv FWF anomaly induces only a small change in the North Atlantic THC, whereas the 1 Sv FWF anomaly induces a near complete shutdown of the overturning circulation. This version of the CCSM is therefore considerably less sensitive to "hosing" than some earlier models were found to be, with significant implications concerning the question as to whether THC collapse should be viewed as a probable consequence of ongoing global warming.
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 3344 Paleoclimatology
DE: 1620 Climate dynamics (3309)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting