Geophysical Research Letters, 36, L05710; doi:10.1029/2008GL036781
Possible oceanic feedback in the extratropics in relation to the North Atlantic SST tripole
Takashi Mochizuki (Frontier Research Center for Global Change, JAMSTEC, Yokohama, Japan), Toshiyuki Awaji (Frontier Research Center for Global Change, JAMSTEC, Yokohama, and Department of Geophysics, Kyoto University, Kyoto, Japan), and Nozomi Sugiura (Frontier Research Center for Global Change, JAMSTEC, Yokohama, Japan)
Abstract
We analyze the results of 4-dimensional variational data assimilation experiments using a coupled general circulation model and identify signals from a possible extratropical oceanic feedback relating to the North Atlantic Sea Surface Temperature (SST) tripole. Examination of the optimized control variables (coupling parameters) and the resultant climate fields reveals that the model errors in the North Atlantic climate variations are very sensitive to the intensity of the extratropical air-sea thermal coupling. This results in the enhancement of the atmospheric responses to SST changes particularly around 40°N, 50°W, when the model errors are most effectively corrected. Since an adjoint approach enables us to detect the sensitivity to fluctuations in the model variables, our results suggest that this oceanic thermal feedback in the extratropics is a key physical process influencing the North Atlantic Oscillation and the associated North Atlantic SST tripole.
Received 24 November 2008, accepted 10 February 2009, published 14 March 2009.
(2009), Possible oceanic feedback in the extratropics in relation to the North Atlantic SST tripole, Geophys. Res. Lett., 36, L05710; doi:10.1029/2008GL036781.
Link to abstract: http://www.agu.org/pubs/crossref/2009/2008GL036781.shtml
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