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  • Methods of oceanographic observation using ships

    • KEIRI Imai, KENJI Oguma, and KOUKI Sawada, Oshoro-maru Marine Science Department, School of Fisheries Sciences, Hokkaido University

       

      Around the beginning of the 16th century, the Age of Exploration, when the rapid development of shipbuilding technology and navigation enabled voyages to the open seas and for longer periods of time, led to the discovery of the Earth as a sphere and the geographical relationship between the oceans and continents, such as the discovery of new continents, which stimulated humanity's exploration of the oceans.

      　In the latter half of the 19th century, several research and survey voyages were undertaken, such as the round-the-world survey voyage by the British ship Challenger, which reported a vast number of results regarding the precise topography of the oceans, the properties of seawater, the geology of the seafloor, and the classification of marine life. At this time, research was conducted using methods that would become the cornerstone of modern ocean observation techniques, and ocean exploration shifted from "adventure" to "ocean observation" to gain scientific knowledge.

      　In the latter half of the 20th century, our understanding of global environmental changes advanced, and the phenomenon of global warming came to be seen as a serious problem. The existence of an atmosphere-ocean interaction, in which greenhouse gases such as carbon dioxide emitted into the atmosphere by human activities since the Industrial Revolution are absorbed from the atmosphere into the oceans or released from the oceans into the atmosphere, is attracting attention. The ocean, which covers 70% of the Earth's surface, is in contact with the atmosphere on all of its surfaces, and the importance of the atmosphere-ocean interaction is now widely recognized when considering the behavior of greenhouse gases. On the other hand, it is reported that over the last 100 years, the average air temperature in Japan has increased by 1.24°C and sea water temperature in the seas around Japan by 1.14°C (Japan Meteorological Agency, 2019). These increases in air and sea water temperatures are minute changes of about 0.01°C per year, and highly accurate and precise observation data are needed to accurately capture small annual changes. Therefore, international cooperation in oceanographic research has led to the development of observation equipment and standardization of observation methods, as well as the planning and execution of numerous oceanographic observations through international joint observation projects. In recent years, unmanned and remote observations using satellites, mooring systems, observation buoys, drifting floats, etc. have been developed, making it possible to obtain a wide range and large amount of data at low human, time, and monetary costs.

      　However, without the use of vessels, it would be impossible to travel to any location on the ocean, obtain samples of seawater, marine organisms, and sediments, or install and retrieve observation equipment. Even in modern times, ships continue to be the primary platform for oceanographic observation. This section introduces some of the most common marine observation methods currently in use on ships.

    • ◀Challenger ship


  • Japan's Ocean Observation Vessels

    •  In Japan, the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Japan Meteorological Agency, Fisheries Agency, Japan Fisheries Research and Education Agency, Japan Coast Guard, Japan Organization for Metals and Energy Security (JOGMEC), and educational institutions such as universities own ships for oceanographic observation. These vessels are given different names such as "observation vessels," "research vessels," "research vessels," "survey vessels," and "training vessels" depending on their purpose, and each voyage is conducted in a way that makes the most of their unique characteristics.


    • みらい

      ◀Ocean Earth Research Vessel "Mirai" （JAMSTEC）

      Mirai is one of the world's most advanced research vessels with observation and research capabilities. Mirai is one of the world's most advanced research vessels, with excellent navigability and ice resistance, and conducts long-term research cruises in a wide range of ocean regions, including the polar regions.






      Courtesy of Japan Agency for Marine-Earth Science and Technology


    • 白鳳丸

      ◀Academic research vessel "Hakuho-Maru" (JAMSTEC)

       Large research vessels featuring a flexible design that can meet a wide variety of research needs. The research voyages are planned and managed jointly by JAMSTEC and the Ocean Research Institute of the University of Tokyo (now the Institute of Atmospheric and Oceanic Studies), which owned the Hakuho Maru until 2004.




      Courtesy of Japan Agency for Marine-Earth Science and Technology


    • ◀Deep Earth Exploration Vessel "Chikyu " (JAMSTEC)

       A vessel that drills the seafloor for the purpose of elucidating the mechanisms of earthquake generation and the sub-seafloor biosphere. The vessel is equipped with riser drilling capabilities to drill to great depths and a transport helipad for long-term drilling operations.



      Courtesy of Japan Agency for Marine-Earth Science and Technology　 (https://www.jamstec.go.jp/chikyu/j/#chikyu-2)


    • しらせ

      ◀Antarctic research vessel (icebreaker) "Shirase" (Japan Maritime Self-Defense Force)

       The Shirase's main mission is to transport observers and supplies to the observation base in Antarctica (Showa Station), and conducts oceanographic observations in the Antarctic Ocean and along the shipping lanes.


      Source:Japan Maritime Self-Defense Force website(https://www.mod.go.jp/msdf/equipment/ships/agb/shirase/)



    • ◀Oceanographic and meteorological observation vessel "Ryofu-Maru" (JMA)

       Performs offshore weather observation operations. Conducts regular oceanographic observations at observation lines established in the northwestern Pacific Ocean and the seas around Japan to monitor changes in the ocean that affect the climate system.


      Source: JMA website (https://www.data.jma.go.jp/gmd/kaiyou/db/vessel_obs/description/vessels.html）


    • ◀Fisheries research vessel "Kaiyo-Maru" (Fisheries Agency)

       A representative fisheries research vessel of the Fisheries Agency, the Kaiyo Maru conducts fisheries resource surveys and investigations of the marine environment that affect trends in fisheries resources.


      Source: Ministry of Agriculture, Forestry and Fisheries Web site (https://www.jfa.maff.go.jp/j/senpaku/ships/kaiyo_maru.html)

    • ◀Fisheries research vessel "Hokko-Maru" (Japan Fisheries Research and Education Agency)

       One of the research vessels belonging to the Fisheries Laboratory. It conducts research related to fisheries, including surveys of fish stocks and plankton that feed on them, as well as monitoring observations of the marine environment.


      Image courtesy of Japan Fisheries Research and Education Agency (https://www.fra.affrc.go.jp/vessel/hokko/)


    • ◀Surveying vessel "Heiyo" (Japan Coast Guard)

       The largest survey vessel of the Japan Coast Guard. Mainly conducts surveys related to seafloor topography, ocean currents, bottom sediments, geomagnetism, etc., which are necessary for charting.


      Source: Japan Coast Guard website

      (https://www1.kaiho.mlit.go.jp/KIKAKU/JCG/images/heiyoL.jpg)

    • 白嶺

      ◀Marine Resources Research Vessel "Hakurei" (JOGMEC)

       Equipped with deep-sea drilling rigs and other research equipment, the vessel explores the seabed resources in the waters around Japan.


      Source:Japan Organization for Metals and Energy Security Web site

      (http://www.jogmec.go.jp/metal/metal_10_000005.html)

    • ◀Training ship "Koyo-Maru" (National Fisheries University)

       In addition to practical training for maritime engineer education, the Koyo Maru conducts various surveys and research on fisheries.



      Image courtesy of Japan Fisheries Research and Education Agency (https://www.fra.affrc.go.jp/vessel/koyo/)


    • ◀Training Ship Oshoro-Maru (おしょろ丸) (Hokkaido University)

       The Oshoro-Maru is equipped with state-of-the-art research and survey equipment to carry out marine and fisheries research. Staff members are stationed on board to operate these facilities and provide cutting-edge technology and research materials to the students on board.



    • (Link: Japanese Vessels Engaged in Ocean Observation)

      　JAMSTEC                        https://www.jamstec.go.jp/j/about/equipment/ships/

      　Antarctic Research Vessel                      https://www.mod.go.jp/msdf/equipment/ships/agb/shirase/

      　Japan Meteorological Agency                            https://www.data.jma.go.jp/gmd/kaiyou/db/vessel_obs/description/vessels.html

      　Fisheries Agency                            https://www.jfa.maff.go.jp/j/senpaku/ships/kaiyo_maru.html

      　Japan Fisheries Research and Education Agency       https://www.fra.affrc.go.jp/vessel/

      　Japan Coast Guard                     https://www1.kaiho.mlit.go.jp/KIKAKU/JCG/msa.html

      　JOGMEC                         http://www.oed.co.jp/product/ship01.html

      　University training ships, etc.

                    Kagoshima University                         https://www.fish.kagoshima-u.ac.jp/aboutus/organization/tvs/

                    Nagasaki University                            http://www.fish.nagasaki-u.ac.jp/FISH/FUZOKU/fuzoku.htm

                    National Fisheries University                         http://www.fish-u.ac.jp/b_rensyusen/top.html

                    Hiroshima University                            https://home.hiroshima-u.ac.jp/toyoshio/

                    Mie University                            http://seisuimaru.bio.mie-u.ac.jp/

                    Tokai University                            https://www.u-tokai.ac.jp/about/research/facilities/bouseimaru/

                    Tokyo University of Marine Science and Technology                     https://www.kaiyodai.ac.jp/overview/facilities/ship/trainingship.html

                    Hokkaido University                         http://ships.fish.hokudai.ac.jp/


  • Types of oceanographic observation methods

     As shown in the "Oshoro-Maru Ocean Observation Chart" below, there are a wide variety of oceanographic observation methods using ships, including towing (towing), placing on the seafloor (mooring), releasing from the ship into the ocean (drifting), and indirect measurement using sound waves, in addition to lowering instruments into the ocean with a wire rope extended from a stationary ship. In this section, we will explain the five main observation methods: (1) CTD observation, (2) biological sampling, (3) water sampling, (4) geological sample collection, and (5) acoustic measurement.



    おしょろ丸　海洋観測図
    おしょろ丸　海洋観測図　Oshoro-Maru Ocean Observation Chart
    北海道大学　Hokkaido University
    海洋調査部　Oshoro-maru Marine Science Department
    科学計量魚群探知機　Scientific Quantitative Fish Finder
    極深海音響測深器　Extreme-Deep-Sea Acoustic Bathymetric Instrument
    ソナードーム　Sonar Dome
    ドップラー式多層流向流速計(ADCP)　Acoustic Doppler Current Profiler
    マルチナロービーム音響測深機　Multi-narrow-beam echo sounder
    CTD採水システム　CTD sampling systems
    自己記録式CTD　Self-recording CTD
    NORPACネット　NORPAC net
    稚魚ネット　Fry nets
    ピンガー　Pinger
    マルチプルコアラ―　Multiple Coaler
    ピストンコアラ―　Piston Coaler
    海底地震計　Seafloor Seismograph
    ORIネット　ORI Net
    MTDネット　MTD Net
    ソリネット　Solinet
    漂流トラップ　Drift trap
    係留系　Mooring system

  • CTD Observation

     Water temperature and salinity are the most fundamental characteristics of seawater, and CTD (Conductivity-Temperature-Depth profiler) observations that measure their vertical distribution are fundamental to ocean observations. This is because water temperature and salinity are not only variables that determine the "density" that governs the dynamics of seawater, but are also important factors that influence biological and chemical processes in the ocean. Furthermore, CTD observations are also essential in the field of acoustic measurement, as represented by bathymetry, to estimate underwater sound velocity and sound wave absorption and attenuation.

    →Method of Ocean Observation (1) CTD Observation

    CTD観測

    CTD採水システム　CTD water sampling system

  • Biological collecting

     Biological specimens have long been collected at marine research sites. During the aforementioned expedition by the Challenger, more than 4,000 species of unknown marine life were discovered. Even today, marine organisms are collected using a variety of methods according to the purpose of the research in order to determine "where" in the ocean "what" organisms exist and "how many" they are. The collected biological samples are used not only for research on the physiology and ecology of individual species, but also to elucidate the interaction between the global environment and marine organisms (ecosystems).

    →Method of Ocean Observation (2) Biological Collection

     

    プランクトンネット　ノルパックネット
    プランクトンネットの一種　A type of plankton net
    NORPACネット　NORPAC net

  • drawing water

    The major component dissolved in seawater is sodium chloride, which is responsible for the salty taste of seawater. In addition, nutrients necessary for phytoplankton growth, gaseous components such as nitrogen, oxygen, and carbon dioxide, organic compounds from various origins, and particulate matter from viruses, bacteria, and minerals are dissolved and mixed to make up seawater. By collecting seawater samples, analyzing their composition, and understanding their distribution in the ocean, we are trying to clarify the environmental dynamics of the oceans and the evolution of the global environment.

    　To collect seawater from a certain layer in the ocean, an instrument called a water sampler is used. The sampler is lowered to the desired depth with the lid open, and the lid is closed on the spot to collect seawater from an arbitrary layer. In addition, seawater is collected by pumping or scooping it up with a bucket. The distribution of seawater components can be continuously determined by measuring the pumped seawater with a sensor or by introducing it directly into an analyzer.

    　As the diversity of analysis items and the accuracy of analysis have increased, water samplers have become larger and larger. While the amount of seawater required for analysis has decreased, it is now necessary to collect more seawater to minimize the effects of contamination. In addition, improvements have been made to the materials and mechanisms of water samplers to prevent even the slightest contamination.

    →Method of Ocean Observation 3) Water sampling

    ニスキン採水器


     

    海水の採取に用いられるニスキン採水器　Niskin water samplers for seawater sampling
    溶存酸素濃度の分析　Analysis of dissolved oxygen concentration
    試水の分取作業(配水)の様子　Sample water sampling operation (water distribution)
    褐色沈殿として固定された溶存酸素　Dissolved oxygen fixed as brown precipitation
    自動滴定装置を用いた溶存酸素の定量分析　Quantitative analysis of dissolved oxygen using autotitrator

  • Geological sampling

     Sedimentary layers are formed on the ocean floor by the accumulation of particles such as mud, sand, and gravel over a long period of time. By collecting sediments from the seafloor and studying their characteristics in detail, we try to decipher the past events (geological events, changes in sea water temperature, etc.) that occurred during the formation of the sedimentary layers, and use this information to predict the future of the global environment. Sediments are also collected for the exploration of resources lying beneath the seafloor and for the collection of organisms living on the seafloor.


     If we look further down in the sedimentary layers, we find a layer of solid rock (the earth's crust). By collecting rocks from the crust and analyzing their chemical composition and structure, we can learn about their formation and degeneration. The distribution characteristics of the rocks that make up the earth's crust are closely related to the plate motions that are believed to cause earthquakes, and it is hoped that the collection of rock samples will help elucidate the mechanisms that generate earthquakes.

    →Method of Ocean Observation (4) Geological sample collection

     

     
    採泥器の一種(マルチプルコアラー)　A type of mud sampler (multiple corer)
    柱状採泥器によって採取された堆積物コア　Sediment core collected by a columnar corer

  • Acoustic Measurement

     Sound waves are often used for remote sensing and data transmission underwater. This is because sound waves propagate much farther than electromagnetic waves (light, radio waves, etc.), which are absorbed and attenuated underwater. The technology to detect sound signals emitted from a ship and bounced back to measure the distance to a distant object is called sonar (SONAR: SOund and NAvigation Ranging) and is indispensable for safe navigation. Sonic exploration technology, which began to develop after the sinking of the Titanic in 1912, is now used not only for depth measurement (distance from the water surface to the seafloor), but also for many underwater acoustic techniques such as fish detection and current velocity measurement, and is used as a means of quickly and extensively monitoring the state of the ocean.


    →Method of Ocean Observation (5) Acoustic Measurement

     



    マルチナロービーム音響測深器による海底地形探査　Seafloor Topographic Survey with Multi-Narrow Beam Acoustic Bathymetry
    計量魚群探知機のエコーグラム　Echogram of a metering fish finder

  • 【Related summary course】