Interdecadal Modulation of the Pacific Decadal Oscillation on the Relationship Between Spring Arctic Oscillation and the Following Winter ENSO

Shangfeng Chen,Jun Ying,Xiaoqing Lan,Yuqiong Zheng,Wen Chen

doi:10.3389/feart.2021.810285

Abstract

Previous studies indicated that Arctic Oscillation (AO) in boreal spring is an important extratropical trigger for the outbreak of El Niño and Southern Oscillation (ENSO) events in the succedent winter. This study reveals that the Pacific Decadal Oscillation (PDO) has a strong modulation on the linkage between the spring AO and the following winter ENSO. Particularly, impact of the spring AO on the succedent winter ENSO is strong during positive PDO phase (+PDO). By contrast, the spring AO-winter ENSO connection is weak during negative PDO phase (−PDO). During +PDO, positive spring AO induces a marked anomalous cyclone over the subtropical North Pacific via wave-mean flow interaction. The subtropical cyclonic anomaly leads to sea surface temperature (SST) warming and enhanced atmospheric heating there, which could further propagate southward to the tropical central Pacific via wind-evaporation-SST feedback mechanism and, thus, impact the following winter El Niño via the tropical process. During −PDO, the spring AO-generated SST, the atmospheric circulation, and the heating anomalies over the North Pacific are much weaker. As such, spring AO has weak impacts on the winter ENSO. The spring climatological storm track is stronger during +PDO than −PDO years due to an increase in the mean meridional temperature gradient over the North Pacific. Stronger storm track intensity during +PDO leads to stronger synoptic-scale eddy feedback to the mean flow, which results in stronger AO-related SST and atmospheric anomalies over the North Pacific and, thus, the stronger impact of the spring AO on the following winter ENSO.

Highlights

The El Niño and Southern Oscillation (ENSO) is the leading atmosphere–ocean coupling pattern over the tropical Pacific on the interannual timescale (Bjerknes, 1969; Philander, 1990; Neelin, 1998; Wang et al, 2000; Chen and Lian 2020; Fang and Xie 2020; Zhang et al, 2020; Hu et al, 2021)
The original contributions presented in the study are included in the article/Supplementary Material
Further inquiries can be directed to the corresponding author

Summary

INTRODUCTION

The El Niño and Southern Oscillation (ENSO) is the leading atmosphere–ocean coupling pattern over the tropical Pacific on the interannual timescale (Bjerknes, 1969; Philander, 1990; Neelin, 1998; Wang et al, 2000; Chen and Lian 2020; Fang and Xie 2020; Zhang et al, 2020; Hu et al, 2021). In brief summary, during +PDO years, spring AO can induce a strong cyclonic anomaly over the subtropical North Pacific via wave-mean flow interaction On one hand, this cyclonic anomaly could directly induce strong westerly wind anomalies over the tropical western Pacific and impact following winter ENSO occurrence via triggering eastward propagating warm equatorial Kelvin wave. According to the findings of previous studies (Jin et al, 2006a, Jin et al, 2006b; Jin, 2010; Chen et al, 2015), stronger climatological storm track over North Pacific during +PDO years would lead to stronger feedback of synoptic-scale eddy activities to low frequency mean flow This explains the stronger atmospheric anomalies over North Pacific in association with the spring AO and, the stronger impact of the spring AO on the following winter ENSO for the +PDO years than the −PDO years. Mean SST and 1,000-hPa air temperature is significantly stronger along west coast of North America with a southwestward extension to the tropical central-eastern Pacific and significantly weaker to the east of Japan around 30°−40°N

SUMMARY

DATA AVAILABILITY STATEMENT