Journal of Oceanography

, Volume 73, Issue 1, pp 25–38 | Cite as

Baroclinic circulation and its high frequency variability in Otsuchi Bay on the Sanriku ria coast, Japan

  • Kiyoshi Tanaka
  • Kousei Komatsu
  • Sachihiko Itoh
  • Daigo Yanagimoto
  • Miho Ishizu
  • Hiroyasu Hasumi
  • Takashi T. Sakamoto
  • Shogo Urakawa
  • Yutaka Michida
Special Section: Original Article Oceanographic observations after the 2011 earthquake off the Pacific coast of Tohoku

Abstract

Hydrographic observations were made in Otsuchi Bay on the Sanriku ria coast, Japan, to provide clear images of the baroclinic circulation extending over the bay together with the associated intrusion of lower-layer water (bottom water) from outside the bay. In summer, a prominent baroclinic circulation with flow speeds \({>} 0.1\ \text{ m }\ \text{ s }^{-1} \) extends over the greater part of the bay. A main pycnocline (thermocline), which separates the upper and lower layers, is located at a depth of 15–40 m in and around the bay. The direction of the lower-layer flow (inflow into and outflow from the bay) is opposite to that of the upper-layer flow, which are baroclinically coupled to each other. Moreover, with regard to the lower-layer flow, the inflow tends to occur mainly through the northwestern part of the bay mouth, whereas the outflow tends to occur mainly through the southeastern part. The inflow and outflow alternate on time scales of several to a few tens of hours, and the flow directions are sometimes related to the tidal ones, although the relationship is not applied persistently. In winter, the baroclinic circulation is considerably weaker than in summer, because the stratification breaks down.

Keywords

Baroclinic circulation High frequency variability  Ria coast Tide Hydrographic observation 

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Copyright information

© The Oceanographic Society of Japan and Springer Japan 2015

Authors and Affiliations

  • Kiyoshi Tanaka
    • 2
  • Kousei Komatsu
    • 1
    • 2
  • Sachihiko Itoh
    • 2
  • Daigo Yanagimoto
    • 2
  • Miho Ishizu
    • 2
  • Hiroyasu Hasumi
    • 2
  • Takashi T. Sakamoto
    • 2
  • Shogo Urakawa
    • 3
  • Yutaka Michida
    • 2
  1. 1.Graduate School of Frontier SciencesThe University of TokyoKashiwa, ChibaJapan
  2. 2.Atmosphere and Ocean Research InstituteThe University of TokyoKashiwa, ChibaJapan
  3. 3.Meteorological Research InstituteJapan Meteorological AgencyTsukuba, IbarakiJapan

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