HR: 08:05h
AN: U31A-01 INVITED     [Abstracts]
TI: Global Warming and the Weakening of the Tropical Circulation
AU: * Vecchi, G A
EM: Gabriel.A.Vecchi@noaa.gov
AF: NOAA/GFDL, Princeton Forrestal Campus Rte. 1 P.O. Box 308 , Princeton, NJ 08542-0308, United States
AU: Soden, B J
EM: bsoden@rsmas.miami.edu
AF: RSMAS University of Miami, Rosenstiel School of Marine and Atmospheric Science University of Miami MPO, MSC 362 4600 Rickenbacker Causeway, Miami, FL 33149, United States
AB: We explore the impact of CO2-induced reduction in the intensity of large-scale atmospheric circulation, resulting from global energetic constraints, on the tropical Pacific atmospheric and oceanic structure and circulation. We examine the projected 21st Century response of the tropical circulation using a set of 22 climate model experiments performed for the IPCC-AR4. In all models there is a robust decrease in the strength of the atmospheric overturning circulation decreases as the climate warms; the circulation weakens in a manner consistent with simple thermodynamic arguments. The weakening occurs preferentially in the zonally-asymmetric (i.e., Walker) rather than zonal-mean (i.e., Hadley) component of the tropical circulation, and results in a weakening the near-equatorial easterlies in the Pacific Ocean. These wind changes induce substantial changes to the thermal structure and circulation of the tropical oceans. Although many aspects of the model changes in both the atmospheric and ocean circulation resemble "El Niño-like" conditions, the mechanisms are shown to be distinct from those of El Niño and are reproduced in both mixed-layer and full ocean dynamics coupled climate models. Even though the mechanisms and structure differ from El Niño, aspects of climate teleconnections (in particular a strengthening of tropical Atlantic vertical wind shear) resemble those associated with El Niño. Changes seen in the consensus of models presented here are also consistent with recently detected changes in the tropical circulation since the 19th Century.
DE: 1620 Climate dynamics (0429, 3309)
DE: 1630 Impacts of global change (1225)
DE: 3374 Tropical meteorology
DE: 4231 Equatorial oceanography
DE: 4504 Air/sea interactions (0312, 3339)
SC: Union [U]
MN: 2007 Joint Assembly