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Possible oceanic feedback in the extratropics in relation to the North Atlantic SST tripole
Author(s) -
Mochizuki Takashi,
Awaji Toshiyuki,
Sugiura Nozomi
Publication year - 2009
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2008gl036781
Subject(s) - extratropical cyclone , north atlantic oscillation , climatology , sea surface temperature , atlantic multidecadal oscillation , data assimilation , environmental science , general circulation model , gulf stream , climate model , atlantic equatorial mode , coupling (piping) , climate change , geology , oceanography , meteorology , physics , mechanical engineering , engineering
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.