Oceanography in Japan
Online ISSN : 2186-3105
Print ISSN : 0916-8362
ISSN-L : 0916-8362
Original Paper
Flow variability with periods of 50-70 days in Sagami Bay, Japan during the offshore non-large-meander path of the Kuroshio
Daisuke Takahashi Akihiko MorimotoTetsuya NakamuraTakuji HosakaYoshihisa MinoToshiro Saino
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2011 Volume 20 Issue 3-4 Pages 59-83

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Abstract

Flow variability in Sagami Bay was examined using mooring data obtained by Project on Ocean Productivity Profiling System (POPPS) buoy during the offshore non-large-meander path (oNLM) of the Kuroshio in 2008. Transition from the nearshore non-large-meander path (nNLM) to oNLM occurred around June 3, 2008, and then the flow field dramatically changed in Sagami Bay. After June 3, 2008, the Kuroshio took the relatively stable oNLM, and the flow variability with periods of 50-70 days whose maximum of amplitude was near 200 m depth was dominated in Sagami Bay. This flow variability was caused by generation of an anticyclonic circulation at a depth of 200 m in the northern part of Sagami Bay, and this generation was associated with the Kuroshio axial variation, which was characterized by S-like shape meander, with periods of about 60 day off the Boso Peninsula. A lense-like structure of 26.2-26.6 σθ isopycnal surfaces at depths of 120-320 m was accompanied by the generation of the anticyclonic circulation, resulting in upwelling of colder lower layer water at depths shallower than 200 m in the northern part of Sagami Bay. When the S-like shape meander vanished off the Boso Peninsula, the anticyclonic circulation inside the lense-Iike isopycnal structure was generated in the northern part of Sagami Bay. Additionally, this Kuroshio axial variation was associated with disturbance with negative sea level anomaly, which was generated around Enshu-nada and propagated eastward. The disturbance arrived off Sagami Bay, and then the S-like shape meander vanished off the Boso Peninsula. Therefore, the anticyclonic circulation in the northern part of Sagami Bay was caused by the Kuroshio axial variation off the Boso Peninsula occurring with the arrival of the disturbance off Sagami Bay, and the generation of the anticyclonic circulation caused the flow variability with periods of 50-70 days in Sagami Bay, which was a typical phenomenon during the oNLM.

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© 2011 the Oceanographic Society of Japan
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