日本財団 図書館


Spatial Structure and Time Evolution of Decadal / Interdecadal Climate Events Observed in the North Pacific

 

Hisashi Nakamura and Toshio Yamagata

Institute for Global Change Research, Frontier Research System for Global Change; also in Department of Earth, Planetary Physics, University of Tokyo.

 

Decadal / interdecadal climate events (DICEs) observed in the North Pacific over the last few decades are documented. Except in the tropics, the observed decadal sea surface temperature (SST) variability in the basin is concentrated in the subarctic and subtropical frontal zones (SAFZ and STFZ, respectively). The decadal SST anomalies in SAFZ are associated with the anomalous Aleutian Low and accompanied by the Pacific / North American (PNA) pattern aloft, whereas those in STFZ are associated with the anomalous subtropical high. The decadal SST fluctuations in STFZ exhibit strong negative simultaneous correlation with the tropical fluctuations but those in SAFZ do not. Neither cooling within SAFZ in the mid-1970s that occurred in advance of tropical warming nor SAFZ warming in the late 1980s can be attributed to the direct tropical influence via atmospheric bridge. In fact, wave activity flux associated with the PNA anomalies is strongly divergent over SAFZ, indicating the PNA is forced there. The associated wind and air temperature anomalies are such that they act to reinforce the SST anomalies by changing heat fluxes, mechanical mixing, Ekman temperature advection and wind stress curl. It is suggested that observed DICEs in the subpolar gyre and atmospheric circulation above could be associated with internally-generated variability in that coupled atmosphere-ocean system, although the associated wind anomalies could influence the subtropical gyre. Lag correlation analysis reveals that significant SST anomalies tend to appear just off the Japanese east coast and Kurile Islands 2〜3 years before the maturity of SST anomalies in SAFZ. As these anomalies in SAFZ weaken, anomalies with the same sign tend to appear in STFZ. In addition to the variability in the North Pacific basin, decadal modulation in the East Asian winter monsoon causes significant decadal SST variability that is confined in the East Chine Sea.

 

 

 

BACK   CONTENTS   NEXT

 






日本財団図書館は、日本財団が運営しています。

  • 日本財団 THE NIPPON FOUNDATION