HR: 0800h
AN: GC51A-0160    [Abstracts]
TI: The Trends of Pacific Shallow Overturning Circulation in Coupled Climate Models
AU: * Zhang, D
EM: dongxiao.zhang@noaa.gov
AF: JISAO/UW and NOAA/PMEL, 7600 Sand Point Way NE, Seattle, WA 98115, United States
AU: McPhaden, M
EM: michael.j.mcphaden@noaa.gov
AF: NOAA/PMEL, 7600 Sand Point Way NE, Seattle, WA 98115, United States
AB: The shallow overturning circulation in the Pacific links subtropical subduction with equatorial upwelling, and is referred to as the Subtropical Cells (STCs). Both observational and modeling studies have indicated the STCs exert a strong influence on equatorial Pacific SST and the decadal modulation of ENSO. We will show that this shallow overturning circulation is significantly correlated with tropical Pacific SST on decadal and multi-decadal time scales during the 20th century in a majority of 14 analyzed coupled climate model simulations. However, the observed slowdown of this circulation in the last 50 years of the 20th century is not well simulated, except in one model (the ocean eddy permitting MIROCH model). On the other hand, studies by Meehl et al. have linked weakening STCs to a change of ENSO amplitudes in global warming scenario runs in two NCAR models, even though the observed STC weakening is not seen in the models' 20th century simulation. More recently, Vecchi et al. have also reported the slow-down of tropical circulation in GFDL models' global warming runs. In this presentation, we will systematically examine how the STCs evolve in long coupled global warming runs and whether the signatures of changing STCs in these models are consistent with the observed in historical record.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1626 Global climate models (3337, 4928)
DE: 4279 Upwelling and convergences (4964)
DE: 4513 Decadal ocean variability (1616, 1635, 3305, 4215)
DE: 4522 ENSO (4922)
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting