Standard Seawater BatCh Offset Table

IAPSO Standard Seawater

The official certified reference material for determining seawater salinities via conductance measurements according to the Practical Salinity Scale (1978) is IAPSO Standard Seawater (SSW), available from Ocean Scientific International Ltd.

Offsets for different batches of Standard Seawater. Note improvements on quality control in recent years.

SSW is produced in numbered batches once or twice a year, with P166 released in 2022.  Although this material is assumed to provide a stable reference if used when not too old, detailed batch-to-batch comparisons performed by independent third parties over the years have found small but systematic changes in the conductance between batches.

In some cases, salinity corrections using these batch offsets improve intercomparisons and trends in long ocean time series, in which different observations have been calibrated against different batches of SSW over time.

Although at present the use of these offsets is not officially endorsed, they are provided here on as ‘as-is’ basis in order to facilitate further scientific investigation. Numerical values are available from the JAMSTEC Data Catalogue at:
 
 

More scientific information about the offset table and its determination  is available from:

  • Uchida, H., M. Oe and M. Wakita (2023): History of batch-to-batch comparative studies of International Association for the Physical Sciences of the Oceans Standard Seawater,  in Chemical reference materials of ocean science: history, production, certification and current status, Akihiko Murata and Cheong Chikako (eds.), Springer, in press)
  • Uchida, H., T. Kawano, T. Nakano, M. Wakita, T. Tanaka and S. Tanihara (2020): An expanded batch-to-batch correction for IAPSO standard seawater. J. Atmos. Oceanic Technol., 37(8), 1507-1520. doi:10.1175/JTECH-D-19-0184.1
  • Kawano, T., M. Aoyama, T. Joyce, H. Uchida, Y. Takatsuki and M. Fukasawa (2006): The latest batch-to-batch difference table of standard seawater and its application to the WOCE onetime sections. J. Oceanogr., 62, 777-792. doi:10.1007/s10872-006-0097-8
  • Mantyla, A. W. (1987): Standard seawater comparisons updated.  J. Phys. Oceanogr., 17(4), 543-548. doi:10.1175/1520-0485(1987)017<0543:SSCU>2.0.CO;2
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