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The IAPSO Standard Sea-Water Service is the only internationally recognized standard for the calibration of salinity measurement devices. Its widespread use over 90 years of IAPSO history has been of great importance to the quality and comparability of salinity data worldwide. IAPSO continues to oversee the preparation of standard sea water and to encourage its use by all laboratories involved in salinity measurement. Demand for this service continues to grow to this day.


  • 1899 Martin Knudsen first recommends a standard seawater to be used in all salinity determinations at the International Council for the Exploration of the Sea (ICES) meeting in Stockholm
  • 1902 First batch of standard seawater produced at the newly created Central Laboratory under direction from Fridtjof Nansen in connection with ICES
  • 1908 New lab opens in Copenhagen under Knudsen to take over production after Nansen decides he no longer wishes to continue
  • 1940 Helge Thomsen takes over the Standard Seawater Service
  • 1947 Frede Herman (Knudsen’s former assistant) takes over the service
  • 1974 Standard Seawater Service transfers to the Institute of Oceanographic Sciences (IOS) in England
  • 1989 Standard Seawater Service, with IAPSO's concurrence, is moved to a private company Ocean Scientific International Limited
  • 1994 Standard Seawater starts to ship in bottles after 90 years of ampoules
  • 2020 There is a complete batch record for every year from 1902 to the current day, the only exceptions being during the First and Second World Wars where collection of Atlantic seawater  was interrupted.  IAPSO Standard Seawaters continue to be available to the oceanographic community globally thorough this service, we currently ship to over 108 countries!