Wintertime Air-Sea Interaction Associated with Recent Decadal Climate Variations In the Northern North Pacific

Over the last two decades, the North Pacific subpolar gyre and overlying atmosphere underwent profound changes on decadal timescales. The East Asian winter monsoon and the Aleutian Low were stronger than normal in the early through mid-1980s, followed by a rather rapid transition into a decadal period of their weakening. Although their nearly simultaneous weakening was probably coincidental, it exerted a substantial impact upon the ocean-atmosphere interaction over that region. The weakening of the Aleutian Low was accompanied by warming within the subarctic frontal zone (SAFZ) and cooling with in the eastern part of the gyre in the late 1980s. Compared to the eastern part of the gyre, the local relation between an SST anomaly and ocean-atmosphere heat exchange seems rather complicated in the SAFZ. The decadal-scale migration of the axis of the SAFZ was almost in phase with the local SST anomalies, but the decadal modulation in its intensity exhibited a lag of 2 or 3 years. The anomalous frontal intensity was contributed to substantially by the polarity reversal of anomalous wind stress curl (but not the stress itself) and an anomaly dipole of the net heat flux that occurred at the surface around the SAFZ.