Decadal Climate Variability in the North Pacific during the Recent Decades

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  • 1 Department of Earth and Planetary Physics, University of Tokyo, Tokyo, Japan
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Decadal wintertime variability in the North Pacific climate system observed over the last few decades is documented. The decadal sea surface temperature (SST) variability is found to be concentrated around two major oceanic fronts. The variability around the subtropical front, accompanied by the anomalous subtropical high, exhibits strong negative simultaneous correlation with the tropical SST variability, but that around the subarctic front does not. In fact, cooling around the subarctic front in the mid-1970s cannot be attributed to the influence through the atmosphere of tropical warming that occurred about two years later. During the coolest period around the subarctic front in the mid-1980s, the enhanced surface westerlies associated with the intensified Aleutian low seemed to reinforce the underlying SST anomalies. The westerlies tended to be substantially weaker during the warmest period around 1970. These findings are suggestive of self-maintaining mechanisms inherent to the northern North Pacific climate system for the decadal variability.

* Additional affiliation: Asian/Pacific Climate Dynamics Division, Frontier Research System for Global Change Prediction, Tokyo, Japan.

Corresponding author address: Hisashi Nakamura, Department of Earth and Planetary Physics, Graduate School of Science, University of Tokyo, Tokyo 113, Japan. E-mail: hisashi@geoph.s.u-tokyo.ac.jp

Decadal wintertime variability in the North Pacific climate system observed over the last few decades is documented. The decadal sea surface temperature (SST) variability is found to be concentrated around two major oceanic fronts. The variability around the subtropical front, accompanied by the anomalous subtropical high, exhibits strong negative simultaneous correlation with the tropical SST variability, but that around the subarctic front does not. In fact, cooling around the subarctic front in the mid-1970s cannot be attributed to the influence through the atmosphere of tropical warming that occurred about two years later. During the coolest period around the subarctic front in the mid-1980s, the enhanced surface westerlies associated with the intensified Aleutian low seemed to reinforce the underlying SST anomalies. The westerlies tended to be substantially weaker during the warmest period around 1970. These findings are suggestive of self-maintaining mechanisms inherent to the northern North Pacific climate system for the decadal variability.

* Additional affiliation: Asian/Pacific Climate Dynamics Division, Frontier Research System for Global Change Prediction, Tokyo, Japan.

Corresponding author address: Hisashi Nakamura, Department of Earth and Planetary Physics, Graduate School of Science, University of Tokyo, Tokyo 113, Japan. E-mail: hisashi@geoph.s.u-tokyo.ac.jp
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