Recent warming in the western North Pacific in relation to rapid changes in the atmospheric circulation of the Siberian high and Aleutian low systems
Résumé
On the basis of a new East Asian winter monsoon (EAWM) index and by analyzing the relationship
between sea surface temperature (SST) anomalies and different atmospheric and oceanic factors in winter,
this study investigates the causes of the recent unusual warming in the western North Pacific Ocean.
Analyses presented here emphasize the dual contribution from the atmosphere and ocean to the local SST
variability, with the relative importance of each contributor varying with the period and place. During the
period 1970–89, the EAWM, controlled mostly by the Siberian high, is predominantly responsible for the
SST variability in most of the western North Pacific, whereas in the period 1990–2005 ocean dynamics
become increasingly important in most places or even dominant in the Kuroshio–Oyasio Extension (KOE)
region. The delayed response of the KOE SST to basinwide wind stress curl forcing via Rossby waves is
epoch dependent and is significant at lags of 1, 3, and 4 yr before 1990 but only at 1 yr afterward. This epoch
dependency of the impact of Rossby waves is related to the different locations of the centers of action of
wind stress curl in the midlatitude North Pacific between the two epochs. In addition, mean advection of the
EAWM-driven anomalous SST from the southern East China Sea, which can be transported into the KOE
region in about a year by the Kuroshio, likely affects the KOE SST lagged by 1 yr. The strongest positive
SST trend observed in the western North Pacific results from the combined effects of the abrupt weakening
of the EAWM due to the unprecedented decline of the Siberian high and the increasing role of the ocean.
The latter is best evidenced by the 1-yr delayed response of the western North Pacific via the gyre circulation adjustment to the basinwide decadal-scale wind stress curl change associated with the northward
shift of the strengthened Aleutian low.
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[15200442 - Journal of Climate] Recent Warming in the Western North Pacific in Relation to Rapid Changes in the Atmospheric Circulation of the Siberian High and Aleutian Low Systems.pdf (3.53 Mo)
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