A Reconstruction of Subtropical Western North Pacific SST Variability Back to 1578, Based on a Porites
 Coral Sr/Ca Record from the Northern Ryukyus, Japan

Abstract 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.

Download Full-text

The influence of wintertime SST variability in the Western North Pacific on ENSO diversity

Climate Dynamics ◽

10.1007/s00382-020-05193-7 ◽

2020 ◽

Vol 54 (7-8) ◽

pp. 3641-3654

Author(s):

Boniface Fosu ◽

Jie He ◽

S.-Y. Simon Wang

Keyword(s):

North Pacific ◽

Western North Pacific ◽

Sst Variability ◽

Enso Diversity

Download Full-text

State Dependence of Atmospheric Response to Extratropical North Pacific SST Anomalies

Journal of Climate ◽

10.1175/jcli-d-15-0672.1 ◽

2017 ◽

Vol 30 (2) ◽

pp. 509-525 ◽

Cited By ~ 7

Author(s):

Guidi Zhou ◽

Mojib Latif ◽

Richard J. Greatbatch ◽

Wonsun Park

Keyword(s):

North Pacific ◽

General Circulation ◽

Western North Pacific ◽

Circulation Model ◽

Atmospheric Response ◽

Mean Flow ◽

Wave Source ◽

Sst Variability ◽

Sst Anomaly ◽

Sst Anomalies

By performing two sets of high-resolution atmospheric general circulation model (AGCM) experiments, the authors find that the atmospheric response to a sea surface temperature (SST) anomaly in the extratropical North Pacific is sensitive to decadal variations of the background SST on which the SST anomaly is superimposed. The response in the first set of experiments, in which the SST anomaly is superimposed on the observed daily SST of 1981–90, strongly differs from the response in the second experiment, in which the same SST anomaly is superimposed on the observed daily SST of 1991–2000. The atmospheric response over the North Pacific during 1981–90 is eddy mediated, equivalent barotropic, and concentrated in the east. In contrast, the atmospheric response during 1991–2000 is weaker and strongest in the west. The results are discussed in terms of Rossby wave dynamics, with the proposed primary wave source switching from baroclinic eddy vorticity forcing over the eastern North Pacific in 1981–90 to mean-flow divergence over the western North Pacific in 1991–2000. The wave source changes are linked to the decadal reduction of daily SST variability over the eastern North Pacific and strengthening of the Oyashio Extension front over the western North Pacific. Thus, both daily and frontal aspects of the background SST variability in determining the atmospheric response to extratropical North Pacific SST anomalies are emphasized by these AGCM experiments.

Download Full-text