Seawater Potential Density Anomaly Referenced to Surface Pressure

Compute the potential density of seawater (minus 1000 kg/m\(^3\)), referenced to surface pressure. This is done using gsw::gsw_sigma0() if eos="gsw", or using swSigmaTheta() if it is "unesco". (The difference between the formulations is typically under 0.01 kg/m^3, corresponding to a few millidegrees of temperature.)

Usage

swSigma0(
  salinity,
  temperature = NULL,
  pressure = NULL,
  longitude = NULL,
  latitude = NULL,
  eos = getOption("oceEOS", default = "gsw")
)

Arguments

salinity: either practical salinity (in which case temperature and pressure must be provided) or an oce object, in which case salinity, temperature (in the ITS-90 scale; see next item), etc. are inferred from the object, ignoring the other parameters, if they are supplied.
temperature: in-situ temperature (\(^\circ\)C), defined on the ITS-90 scale. This scale is used by GSW-style calculation (as requested by setting eos="gsw"), and is the value contained within ctd objects (and probably most other objects created with data acquired in the past decade or two). Since the UNESCO-style calculation is based on IPTS-68, the temperature is converted within the present function, using T68fromT90().
pressure: pressure (dbar)
longitude: longitude of observation (only used if eos="gsw"; see “Details”).
latitude: latitude of observation (only used if eos="gsw"; see “Details”).
eos: equation of state, either "unesco" (references 1 and 2) or "gsw" (references 3 and 4).

Value

Potential density anomaly (kg/m\(^3\)).

References

See citations provided in the swRho() documentation.

Other functions that calculate seawater properties: T68fromT90(), T90fromT48(), T90fromT68(), computableWaterProperties(), locationForGsw(), swAbsoluteSalinity(), swAlpha(), swAlphaOverBeta(), swBeta(), swCSTp(), swConservativeTemperature(), swDepth(), swDynamicHeight(), swLapseRate(), swN2(), swPressure(), swRho(), swRrho(), swSCTp(), swSR(), swSTrho(), swSigma(), swSigma1(), swSigma2(), swSigma3(), swSigma4(), swSigmaT(), swSigmaTheta(), swSoundAbsorption(), swSoundSpeed(), swSpecificHeat(), swSpice(), swSpiciness0(), swSpiciness1(), swSpiciness2(), swSstar(), swTFreeze(), swTSrho(), swThermalConductivity(), swTheta(), swViscosity(), swZ()

Author

Dan Kelley