HR: 0800h
AN: PP31A-0902    [Abstracts]
TI: ENSO Response to a Change in Thermohaline Circulation Caused by Surface Fresh Water Forcing of the North Atlantic Basin
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: 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: 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: Previous studies of the coupled atmosphere-ocean response of the climate system to collapse of the North Atlantic thermohaline circulation (THC), and subsequent cooling of the northern hemisphere, have alluded to, though not established, the existence of a possible connection to Tropical Pacific climate variability. A series of fresh water forcing (FWF) anomalies of 0.1 and 1Sv, each of 100 years duration, have been applied to the surface of the North Atlantic between 50 and 70 degrees north latitude in an equilibrated NCAR CCSM1.4 modern pre-industrial simulation which fully resolves the ENSO process. The climate is allowed to readjust after this forcing is removed. The changes in both the atmosphere and oceans that result in a strengthened ENSO during the transient period of THC collapse caused by the freshwater forcing will be described. Of particular interest is the existence of an atmospheric teleconnection between the North Atlantic and the Tropical Pacific, whereby a PNA type pattern induced by a quasi-stationary train of planetary Rossby waves modifies the surface wind stresses in the tropical Pacific. This sets up in concert with a significant increase in the strength of the Hadley circulation of the tropical atmosphere. The increase in the strength of both the ENSO process and the Hadley circulation are essentially identical to those previously found to be characteristic of Last Glacial Maximum conditions (Peltier and Solheim, QSR 23, 335-357, 2004). A number of results will be presented that attempt to resolve the issue as to whether the tropical system is solely responding to a Northern Hemisphere cooling or whether a feedback mechanism might exist that modifies both the tropical Pacific and Northern Hemisphere climate regimes.
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