Wind- and density-driven circulation in a bay on the Sanriku ria coast, Japan: study of Shizugawa Bay facing the Pacific Ocean

Daisuke Takahashi, Hikaru Endo, Yuki Minegishi, Yasushi Gomi, Kenji Kaneko

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Flow fields in Shizugawa Bay on the Sanriku ria coast, which faces the Pacific Ocean, were investigated using hydrographic observations for the purpose of understanding oceanographic conditions and the process of water exchanges in the bay after the 2011 earthquake off the Pacific coast of Tohoku. In spring to summer, density-driven surface outflow is part of estuarine circulation and is induced by a pressure gradient force under larger longitudinal gradients in density along with lower salinity water in the innermost part of the bay, regardless of wind forcing. In winter to summer, another density-driven current with a thermal structure is induced by a pressure gradient force under the smaller longitudinal density gradients in calm wind conditions. Particularly in winter, Tsugaru Warm Current water can be transported in the surface layer inside the bay. Wind-driven bay-scale circulation with downwind and upwind currents in the surface and deeper layers, respectively, is induced by strong longitudinal wind forcing under the smaller longitudinal density gradients, irrespective of season. Particularly in fall to spring, this circulation can cause the intrusions of oceanic water associated with Oyashio water and Tsugaru Warm Current water in the deeper layer. These results suggest that wind- and density-driven currents can produce the active exchange of water from inside and outside the bay throughout the year.

Original languageEnglish
Pages (from-to)81-100
Number of pages20
JournalJournal of Oceanography
Volume74
Issue number1
DOIs
Publication statusPublished - 2018 Feb 1

Keywords

  • Density-driven current
  • Estuarine circulation
  • Hydrographic observation
  • Intrusion of oceanic water
  • Sanriku ria coast
  • Shizugawa Bay
  • Wind-driven circulation

ASJC Scopus subject areas

  • Oceanography

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