Regeneration of a warm anticyclonic ring by cold water masses within the western subarctic gyre of the North Pacific

Sachihiko Itoh, Ichiro Yasuda, Hiromichi Ueno, Toshio Suga, Shigeho Kakehi

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Regeneration of a warm anticyclonic ring as a result of interaction with cold water masses was observed within the western subarctic gyre of the North Pacific. Satellite, profiling float, and shipboard observations revealed that a warm-core ring originated from the Kuroshio Extension, propagating northeastwards, entrained cold and fresh water masses from the coastal area of Hokkaido, which are typically recognized within the ring as water that is colder than 2.5 °C. The potential temperature and planetary contribution of potential vorticity of the cold water in the coastal area of Hokkaido were <2 °C and 15 × 10-11 m-1s-1, respectively, suggesting that it originated from the Sea of Okhotsk. After the intrusion, the warm core of the ring cooled, freshened, and contracted, while the outer and lower parts became occupied by the cold and fresh water; however, even after the cooling, the positive surface elevation and downward depression of the main pycnocline, typical of an anticyclonic ring, were still evident. The ring continued to propagate northeastwards, with the main part of its structure occupied by the cold water, but changed its direction of travel from northwest to west-southwest 8 months after the cold-water event, and was finally absorbed into another warm-core ring. It is suggested that these anticyclonic rings, which transported and mixed warm and cold water masses, play important roles in the cross-gyre exchange of subtropical and subarctic waters in the North Pacific.

Original languageEnglish
Pages (from-to)211-223
Number of pages13
JournalJournal of Oceanography
Volume70
Issue number3
DOIs
Publication statusPublished - 2014 Jan

Keywords

  • Anticyclonic ring
  • Cold core
  • Cross-gyre exchange
  • Kuroshio
  • Profiling float
  • Regeneration
  • Sea of Okhotsk
  • Warm core

ASJC Scopus subject areas

  • Oceanography

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