R: Seawater spiciness

swSpice {oce} | R Documentation

## Seawater spiciness

### Description

Compute seawater "spice", also called "spiciness" (a variable orthogonal to density in TS space), in either of two formulations, depending on the value of the `eos` argument. If `eos="unesco"` then Flament's (reference 1) formulation is used. If `eos="gsw"` then the Gibbs SeaWater formulation for "spiciness0" is used (see reference 2).

### Usage

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

### Arguments

`salinity` | either salinity (PSU) (in which case `temperature` and `pressure` must be provided) or a `ctd` object (in which case `salinity`, `temperature` and `pressure` are determined from the object, and must not be provided in the argument list).
`temperature` | in-situ temperature (degC) on the ITS-90 scale; see “Temperature units” in the documentation for `swRho()`.
`pressure` | Seawater pressure (dbar) (only used if `eos` is `"gsw"`); see ‘Details’..
`longitude` | longitude of observation (only used if `eos` is `"gsw"`; see ‘Details’).
`latitude` | latitude of observation (only used if `eos` is `"gsw"`; see ‘Details’).
`eos` | Character value specifying the equation of state, either `"unesco"` (for the Flament formulation, although this is not actually part of UNESCO) or `"gsw"` for the Gibbs SeaWater formulation.

### Details

If the first argument is a `ctd` object, then salinity, temperature and pressure values are extracted from it, and used for the calculation. (For the `eos="gsw"` case, longitude and latitude are also extracted, because these are required for the formulation of spiciness0.

Roughly speaking, seawater with a high spiciness is relatively warm and salty compared with less spicy water. Another interpretation is that spice is a variable measuring distance orthogonal to isopycnal lines on TS diagrams (if the diagrams are scaled to make the isopycnals run at 45 degrees). Note that pressure, longitude and latitude are all ignored in the Flament definition.

### Value

Flament-formulated spice kg/m^3 if `eos` is `"unesco"` or surface-referenced GSW spiciness0 kg/m^3 if `eos` is `"gsw"`, the latter provided by `gsw::gsw_spiciness0()`, and hence aimed at application within the top half-kilometre of the ocean.

### Author(s)

Dan Kelley coded this, merely an interface to the code described by references 1 and 2.

### References

1. Flament, P. “A State Variable for Characterizing Water Masses and Their Diffusive Stability: Spiciness.” Progress in Oceanography, Observations of the 1997-98 El Nino along the West Coast of North America, 54, no. 1 (July 1, 2002):493-501. https://doi.org/10.1016/S0079-6611(02)00065-4

2.McDougall, Trevor J., and Oliver A. Krzysik. “Spiciness.” Journal of Marine Research 73, no. 5 (September 1, 2015): 141-52. https://doi.org/10.1357/002224015816665589

### See Also

Other functions that calculate seawater properties: `T68fromT90()`, `T90fromT48()`, `T90fromT68()`, `swAbsoluteSalinity()`, `swAlphaOverBeta()`, `swAlpha()`, `swBeta()`, `swCSTp()`, `swConservativeTemperature()`, `swDepth()`, `swDynamicHeight()`, `swLapseRate()`, `swN2()`, `swPressure()`, `swRho()`, `swRrho()`, `swSCTp()`, `swSTrho()`, `swSigma0()`, `swSigma1()`, `swSigma2()`, `swSigma3()`, `swSigma4()`, `swSigmaTheta()`, `swSigmaT()`, `swSigma()`, `swSoundAbsorption()`, `swSoundSpeed()`, `swSpecificHeat()`, `swTFreeze()`, `swTSrho()`, `swThermalConductivity()`, `swTheta()`, `swViscosity()`, `swZ()`

### Examples

    ## Contrast the two formulations.
    library(oce)
    data(ctd)
    p <- ctd[["pressure"]]
    plot(swSpice(ctd, eos="unesco"), p,
         xlim=c(-2.7, -1.5), ylim=rev(range(p)),
         xlab="Spice", ylab="Pressure (dbar)")
    points(swSpice(ctd, eos="gsw"), p,col=2)
    mtext("black=unesco, red=gsw")

[Package oce version 1.2-0 Index]