Climate Dynamics

, Volume 53, Issue 11, pp 7011–7025 | Cite as

On the seasonal variability of the Oyashio extension fronts

  • Baolan Wu
  • Xiaopei LinEmail author
  • Bo Qiu


Previous study reported that the annual-mean eastern Oyashio Extension (OE) front shifts northward while the western OE front has no obvious poleward shift during 1982–2017 by Wu et al. (Geophys Res Lett 45:9042–9048, 2018). Here we revisit this topic and focus on the seasonal variability and shifts of the OE fronts from 1982 to 2018, with observational reanalysis data and a 1.5-layer reduced-gravity model simulation. In winter, both the western and eastern OE fronts demonstrate consistent northward movement. While in summer, the eastern OE front still moves northward but the western OE front has no obvious and even southward shift. It is shown that the trade wind’s expansion during 1982–2018 favours the northward shift of the OE fronts for both winter and summer. However, there is a local cold Ekman heat transport anomaly along the western OE front in summer, which surpasses the effect of trade wind expansion and prohibits northward movement of the front. This cold Ekman advection is due to a westerly wind anomaly induced firstly by the Atlantic Multi-decadal Oscillation (AMO) and secondly by the Pacific Decadal Oscillation (PDO). In winter, the local Ekman heat transport is less effective than in summer in changing the OE front position because of the deep mixed layer. Our study demonstrates the seasonality of the OE front shift and highlights the importance of local Ekman heat transport associated with the AMO. Our results also partly explain the rainfall changes in both winter and summer in the western Pacific Ocean in the past 37 years, since the rainband east of Japan is affected by the sea surface temperature and its front.



Xiaopei Lin is supported by the China’s national key research and development projects (2016YFA0601803), the Qingdao National Laboratory for Marine Science and Technology (2017ASKJ01) and the National Natural Science Foundation of China (41490641, 41521091 and U1606402). The software used to generate all the results in this study is MATLAB.

Supplementary material

382_2019_4972_MOESM1_ESM.docx (4.9 mb)
Supplementary material 1 (DOCX 4978 kb)


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Physical Oceanography Laboratory/Institute for Advanced Ocean StudyOcean University of China and Qingdao National Laboratory for Marine Science and TechnologyQingdaoChina
  2. 2.Department of OceanographyUniversity of Hawaii at ManoaHonoluluUSA

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