HR: 09:45h
AN: PP21A-08    [PDF]
TI: An atmospheric bridge mechanism for sea ice influence on the position of the marine ITCZ
AU: * Chiang, J C
EM: jchiang@atmos.berkeley.edu
AF: Dept of Geography, University of California, 547 McCone Hall, Berkeley, CA 94720-4740 United States
AU: Bitz, C M
EM: bitz@apl.washington.edu
AF: Polar Science Center, Applied Physics Laboratory, 1013 NE 40th St, Seattle, WA 98105 United States
AB: We identify a mechanism for high latitude sea ice influence on the meridional position of the marine ITCZ in the Community Climate model version 3 coupled to a simple slab ocean model. The marine ITCZ in all three ocean basins shift meridionally away from the hemisphere with imposed additional sea ice. The impact on the ITCZ does not appear to depend on the longitudinal position, nor the hemisphere, of the additional sea ice. Examination of the zonal mean transient response shows the apparent propagation of cooler atmospheric temperature and humidity anomalies, and cooler surface temperature anomalies, from the high latitudes of the additional sea ice to the equator. When the anomalies reach ITCZ latitudes, the resulting meridional gradient in SST formed across that latitude shifts the ITCZ away from the hemisphere with increased sea ice. The resulting change to the Hadley circulation transports moisture away from the drier hemisphere into the moister hemisphere, creating a positive feedback that amplifies the hemispheric asymmetry in atmospheric moisture. We discuss the potential relevance of this mechanism to the 'real' climate, in particular as a candidate for communicating high latitude climate changes to the tropics in the paleoclimate, and also as an influence to present day interannual-decadal variability.
DE: 1620 Climate dynamics (3309)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting