Climatological mean features and interannual to decadal variability of ring formations in the Kuroshio Extension region

  • Yoshi N. SasakiEmail author
  • Shoshiro Minobe


This study examines the climatological mean features of oceanic rings shed from the Kuroshio Extension (KE) jet and their interannual to decadal variability using satellite altimeter observations from October 1992 to December 2010. To objectively capture ring shedding from the KE jet, a new method that consists of the detection of the jet length changes and the tracking of a ring is proposed. Spatial distribution of the ring formations in the KE region indicates that cyclonic (cold-core) rings were most frequently formed in the upstream region between 143° and 147°E around the steady meander of the KE jet. In contrast, most of anticyclonic (warm-core) rings were formed in the downstream region west of the Shatsky Rise. These pinched-off rings in both the upstream and downstream regions generally propagated westward, but about two-thirds of the rings were reabsorbed by the jet. Nevertheless, about one-fourth of the meridional eddy heat transport at the latitude of the KE resulted from the rings that are not reabsorbed by the jet. The number of ring formations showed substantial interannual to decadal variability. In the upstream and downstream KE region, decadal and interannual variability was dominant, respectively. These ring formation fluctuations were negatively correlated with the strength of the KE jet. It is also revealed that the ring formation variations play an important role in sea surface temperature changes north of the KE jet.


Kuroshio Extension Pinch-off ring Jet Heat transport Interannual to decadal variability 



We thank two anonymous reviewers for comments that helped improve the manuscript. This research was supported by a Grant-in-Aid for Scientific Research on Innovative Areas (Grant Number 22106008) and a Grant-in-Aid for Young Scientists (Grant Number 25800258), wholly funded by the Ministry of Education, Culture, Sports, Science, and Technology of Japan.


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Copyright information

© The Oceanographic Society of Japan and Springer Japan 2016

Authors and Affiliations

  1. 1.Science 8th bldg 8-3-20, Graduate School of ScienceHokkaido UniversitySapporoJapan

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