Oceanography in Japan
Online ISSN : 2186-3105
Print ISSN : 0916-8362
ISSN-L : 0916-8362
Volume 20 , Issue 3-4
Showing 1-3 articles out of 3 articles from the selected issue
Rapid Communication
  • Shigeho Kakehi
    Type: rapid-communication
    2011 Volume 20 Issue 3-4 Pages 51-57
    Published: July 15, 2011
    Released: April 09, 2020
    JOURNALS FREE ACCESS

    The great earthquake, the epicenter of which was off Miyagi Prefecture, occurred at 14:46 JST, 11 March 2011. Tsunamis triggered by the earthquake reached and induced destructive damage to the coastal area. The sea level variations due to tsunamis were recorded using the wave height meter settled on Shichigahama, Miyagi. Although the true peak of tsunami might not be observed because the measurement was conducted at 10-minute intervals, large tsunamis up to 2 meter referred to the mean sea level were recorded several times. The maximum tsunami with a wave height greater than 6.19 meter was observed at 16:00. The sea level variations due to the tsunami continued for at least 5 days. Since the mean sea level after the earthquake ascended at 0.30 meter,the occurrence of land subsidence was indicated.

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Original Paper
  • Daisuke Takahashi, Akihiko Morimoto, Tetsuya Nakamura, Takuji Hosaka, ...
    Type: research-article
    2011 Volume 20 Issue 3-4 Pages 59-83
    Published: July 15, 2011
    Released: April 09, 2020
    JOURNALS FREE ACCESS

    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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  • Sachiko Oguma, Tomonori Azumaya, Shigeru Montani, Mitsuhiro Nagata
    Type: research-article
    2011 Volume 20 Issue 3-4 Pages 85-100
    Published: July 15, 2011
    Released: April 09, 2020
    JOURNALS FREE ACCESS

    We estimated sea water budget caused by vertical mixing and vertical advection in Nemuro Bay using oceanographic data obtained from April to July in 2007 and 2008. Based on vertical distributions of temperature and salinity, we applied two-layer box model adjusting to heat and salinity budgets between inside and outside of Nemuro Bay. It was also examined how the difference between thermal and salinity diffusion affects to vertical transport of sea water. Vertical volume fluxes caused by vertical mixing and vertical advection were 1.05 - 13.10 X 103 m3 s-1 and -0.15 - 0.09 X 103 m3 s-1 in 2007 and 0.92 - 18.73 X 103 m3 s-1 and -0.03 - 0.07 X 103 m3 s-1 in 2008. It was suggested that vertical mixing as well as horizontal mixing largely contributed among the processes of sea water transport in Nemuro Bay.

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