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    • Why measure seawater temperature and salinity? ページ

      Since the vertical movement and mixing of seawater is governed by density differences, the movement of water has been studied from the density differences of water by measuring salinity and water temperature.

      Water masses in a given area and at a given depth have a certain characteristic (unique) range of salinity and temperature. To understand the movement and mixing of water masses, it is fundamental to investigate water temperature and salinity.



    • Scenes from CTD observations on the training ship "Ushio-Maru" (LASBOS Youtube video)

      The CTD instrument measures Conductivity, Temperature, and Depth, so it is called a CTD instrument. There is also an option to simultaneously measure the phytoplankton pigment chlorophyll and oxygen concentration. Along with the CTD, a bottle to sample seawater is sometimes included. The video below shows a CTD-only observation. On the Funka-Bay observation (Ushio-Maru), students do deck work for CTD observations. There are not many research and training vessels where students are at the forefront of deck work.


      CTD observation (video below: 41MB)

      （Observations by the School of Fisheries Sciences, Hokkaido University.）
      Search "Youtube LASBOS hokudai" to view related videos, including this one.
    • T-S diagram of representative currents and water masses in the Pacific Ocean near Japan ページ

      　An X-Y plot of seawater temperature (T) and salinity (S) measured along an observation line (vertical or horizontal) is called a T-S diagram.

      　Each water mass has its own characteristic plot. This is useful for classifying water masses and studying the movement and mixing of water masses, so let's use the T-S diagram around Japan as an example to understand the characteristics of the subtropical and subarctic and their transition regions in the Northwest Pacific.

      Figure 1

    • Subarctic and subtropical of the North Pacific surface ページ

      Roughly, a density of less than 26.7σ is considered a surface layer. The surface layer is the combination of the surface mixed layer and the subduction layer. The subtropical has a thick surface layer and the subarctic has a thin surface layer. The subarctic and subtropical of the North Pacific are divided by a salinity of 34.

      Figure 2

    • Water temperature and salinity range in the transition region between the Oyashio and Kuroshio currents (mixed waters) ページ

      Understand the water temperature and salinity range of the Oyashio and Kuroshio currents transition regions.

      Figure 3

    • Link to Japan Meteorological Agency (Knowledge of Ocean Temperature and Currents > Oyashio Front, Kuroshio Front, and Mixed Region) URL

      Learn about the ocean on the Japan Meteorological Agency (JMA) website as well.

    • Link to JAMSTEC "Kuroshio Oyashio Watch" URL
      This is a predictability experiment and information provided by the JAMSTEC Application Lab along the coast of Japan.
    • Link to the Japan Coast Guard Maritime Information Department's "Teach Us! "Umimaru" website URL

      The Japan Coast Guard also provides detailed information on ocean currents and tides.

    • Distribution of fishery resources and TS distribution (Supplement) ページ

      Fisheries resources (e.g., fish) are also distributed according to the distribution of water temperature.

      Figure 4