HR: 08:40h
AN: A41F-03    [Abstracts]
TI: Teleconnection mechanisms to the tropical Atlantic sector from climate changes following an abrupt freshening of the North Atlantic
AU: * Chiang, J C
EM: jchiang@atmos.berkeley.edu
AF: University of California, 547 McCone Hall, Berkeley, CA 94720-4740, United States
AU: Cheng, W
EM: wcheng@ocean.washington.edu
AF: NOAA/PMEL, 7600 Sand Point Way NE, Seattle, WA 98115, United States
AU: Bitz, C M
EM: bitz@atmos.washington.edu
AF: University of Washington, Atmospheric Sciences Building, Seattle, WA 98195, United States
AB: Distinct ocean dynamical and atmospheric teleconnection pathways have been previously proposed to explain the pronounced response of the tropical North Atlantic climate - in particular, a southward shift of the Intertropical Convergence Zone (ITCZ) - to high latitude North Atlantic climate changes resulting from forced slowdowns of the Atlantic Meridional Overturning Circulation (AMOC). The climate adjustment to an abrupt freshening of the high Northern Atlantic in an ensemble of Community Climate System Model 3 simulations shows both ocean and atmospheric mechanisms at work to cool the midlatitude North Atlantic sea surface temperatures. In the north tropical Atlantic (NTA) however, atmospheric-mediated teleconnection associated with wind-evaporation-SST feedback dominates the cooling, whereas subsurface ocean dynamical response appears to warm the NTA, countering the atmospheric cooling. Thus, atmospheric mechanisms appear to be responsible for the southward ITCZ displacement in AMOC-slowdown scenarios, though our analysis also suggest that the magnitude of this displacement may depend on the relative strengths of the atmospheric and oceanic responses in the NTA. The mechanisms influencing NTA SST in the AMOC slowdown appear distinctly different from the ENSO/NAO-driven trade wind paradigm for interannual SST variations, and may suggest new avenues for understanding tropical Atlantic variability in particular on longer timescales.
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 3309 Climatology (1616, 1620, 3305, 4215, 8408)
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly