Sections below: Temperature | Salinity | Oxygen | Nutrients | Depth

Units used in CARS and BOA

This page describes the units used for properties represented in CARS (CSIRO Atlas of Regional Seas), and BOA (BLUELink Ocean Archive).



Temperature

Temperature is in degrees Celsius. However, there are different definitions of temperature in seawater, and modern observations are reported in a standard called ITS-90. Ideally BOA and CARS would be standardized on ITS-90, but they are not. Temperature has been collated and mapped using the values as found in the source datasets.

Conversions between the standards are discussed here .

World Ocean Database is the largest data source used in BOA. For CARS2009, the WOD2005 was used with the July 2008 Update. The documentation for WOD has this to say:
Temperature measurements have been obtained by means of manual (i.e., visual readings of temperature from reversing thermometers) and automated (i.e., digital recordings of temperature from STDs and CTDs) instruments. Temperature measurements have been obtained following several International Temperature Scales (ITSITS-1927; ITS-1948, ITS-1968) to the ITS-1990 (Preston-Thomas, 1990). Temperature data in WOD09 nominal units are in the scale the measurements were reported in by the originator of the data.

CSIRO data, directly sourced from CSIRO rather than via WOD, is already standardised (including pre-1990 data) to ITS-90.

WOCE data does identify the standard used for temperature in each file, so this could (and will in future) be used to standardise on ITS-90.



Salinity

Salinity is in Practical Salinity Units (PSU). Again, it is used as found in hte source datasets.

Standards blah blah

World Ocean Database
Salinity measurements have been obtained by manual (e.g., chemical titrations, chlorinity to salinity formulae, refractometers, salinographs, inductive salinometers, etc.) and automated (i.e., conductivity to salinity from CTDs) methods. For the past few decades, bottle salinity sampling and analyses are normally conducted to calibrate the conductivity to salinity measurements of CTDs. Salinity measurements have been obtained using reference standard seawater samples of known salinity (within uncertainty). In 1978 the practical salinity scale (PSS-1978) was adopted defining salinity in terms of electrical conductivity ratio (UNESCO, 1981; Lewis and Perkins, 1981; Culkin and Ridout, 1998). Under the PSS-1978 definition, salinity measurements are dimensionless (Millero, 1993). Seawater standards provide a means to test the calibration of salinity measurement instruments and facilitate the inter-comparison of ocean salinity measurements against samples of known electrical conductivity ratio (UNESCO, 1981; Mantyla, 1980; 1987; 1994; Culkin and Smed, 1979; Culkin, 1986; Aoyama et al., 2002; Kawano et al., 2005; Saunders, 1986). More recently, the concept of absolute salinity anomaly has been introduced to compute absolute salinity values in terms of salinity values using the PSS-78 definition (McDougall et al., 2009). In all cases, WOD09 salinity data are not corrected for ?standard sea water? changes (Mantyla, 1994) or converted to any salinity scale other than the scale the measurements were reported in.

UNDER CONSTRUCTION

 

Legal Notice and Disclaimer | Copyright | Privacy | Last modified: 6/8/2010 | Page author: Jeff Dunn | Contact: Jeff.Dunn@csiro.au