Endorsed by
Unesco/SCOR/ICES/lAPSO Joint Panel
on Oceanographic Tables and Standards
and SCOR Working Group 51

Algorithms for the computation of fundamental properties of seawater.

Correlations and data for the thermophysical properties of seawater are reviewed. Properties examined include density, specific heat capacity, thermal conductivity, dynamic viscosity, surface tension, vapor pressure, boiling point elevation, latent heat of vaporization, specifi c enthalpy, specific entropy and osmotic coefficient. These properties include those needed for design of thermal and membrane desalination processes. Results are presented in terms of regression equations as functions of temperature and salinity. The available correlations for each property are summarized with their range of validity and accuracy. Best-fi tted new correlations are obtained from available data for density, dynamic viscosity, surface tension, boiling point elevation, specifi c enthalpy, specific entropy and osmotic coefficient after appropriate conversion of temperature and salinity scales to the most recent standards. In addition, a model for latent heat of vaporization is suggested. Comparisons are carried out amo...

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Thermophysical properties of seawater: a review of existing correlations and data

The thermophysical properties of seawater: A review of existing correlations and data

Fundamental determinations of the physical properties of seawater have previously been made for Atlantic surface waters, referred to as “Standard Seawater”. In this paper a Reference Composition consisting of the major components of Atlantic surface seawater is determined using these earlier analytical measurements. The stoichiometry of sea salt introduced here is thus based on the most accurate prior determination of the composition, adjusted to achieve charge balance and making use of the 2005 atomic weights. Reference Seawater is defined as any seawater that has the Reference Composition and a new Reference-Composition Salinity S R is defined to provide the best available estimate of the Absolute Salinity of both Reference Seawater and the Standard Seawater that was used in the measurements of the physical properties. From a practical point of view, the value of S R can be related to the Practical Salinity S by S R = ( 35.16504 / 35 ) g kg - 1 × S . Reference Seawater that has been “normalized” to a Practical Salinity of 35 has a Reference-Composition Salinity of exactly S R =35.16504 g kg −1 . The new independent salinity variable S R is intended to be used as the concentration variable for future thermodynamic functions of seawater, as an SI-based extension of Practical Salinity, as a reference for natural seawater composition anomalies, as the currently best estimate for Absolute Salinity of IAPSO Standard Seawater, and as a theoretical model for the electrolyte mixture “seawater”.

The composition of Standard Seawater and the definition of the Reference-Composition Salinity Scale

[1] Discretization of the pressure-gradient force is a long-standing problem in terrain-following (or σ) coordinate oceanic modeling. When the isosurfaces of the vertical coordinate are not aligned with either geopotential surfaces or isopycnals, the horizontal pressure gradient consists of two large terms that tend to cancel; the associated pressure-gradient error stems from interference of the discretization errors of these terms. The situation is further complicated by the nonorthogonality of the coordinate system and by the common practice of using highly nonuniform stretching for the vertical grids, which, unless special precautions are taken, causes both a loss of discretization accuracy overall and an increase in interference of the component errors. In the present study, we design a pressure-gradient algorithm that achieves more accurate hydrostatic balance between the two components and does not lose as much accuracy with nonuniform vertical grids at relatively coarse resolution. This algorithm is based on the reconstruction of the density field and the physical z coordinate as continuous functions of transformed coordinates with subsequent analytical integration to compute the pressure-gradient force. This approach allows not only a formally higher order of accuracy, but it also retains and expands several important symmetries of the original second-order scheme to high orders [Mellor et al., 1994; Song, 1998], which is used as a prototype. It also has built-in monotonicity constraining algorithm that prevents appearance of spurious oscillations of polynomial interpolant and, consequently, insures numerical stability and robustness of the model under the conditions of nonsmooth density field and coarse grid resolution. We further incorporate an alternative method of dealing with compressibility of seawater, which escapes pressure-gradient errors associated with interference of the nonlinear nature of equation of state and difficulties to achieve accurate polynomial fits of resultant in situ density profiles. In doing so, we generalized the monotonicity constraint to guarantee nonnegative physical stratification of the reconstructed density profile in the case of compressible equation of state. To verify the new method, we perform traditional idealized (Seamount) and realistic test problems.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2001JC001047

A method for computing horizontal pressure-gradient force in an oceanic model with a nonaligned vertical coordinate

A new high pressure equation of state for water and seawater has been derived from the experimental results of Millero and coworkers in Miami and Bradshaw and Schleicher in Woods Hole The form of the equation of state is a second degree secant bulk modulus 
K = Pv0(v0−vp=K0+AP+BP2

K = Kw0+aS+bS32

A = Aw+cS+dS32

B = Bw+eS
where ν0 and νP are the specific volume at 0 and P applied pressure and S is the salinity (ℵ) The coefficients KWO, AW, and BW for the pure water part of the equation are polynomial functions of temperature The standard error of the pure water equation of state is 43 × 10−6 cm3 g−1 in νWP The temperature dependent parameters a, b, c, d, and e have been determined from the high pressure measurements on seawater The overall standard error of the seawater equation of state is 90 × 10−6 cm3 g−1 in νP Over the oceanic ranges of temperature, pressure, and salinity the standard error is 50 × 10−6 cm3 g−1 in νP This new high pressure equation of state has recently (1979) been recommended by the UNESCO Joint Panel on Oceanographic Tables and Standards for use by the oceanographic community

A new high pressure equation of state for seawater

(1982). A new high pressure equation of state for seawater. Marine Geodesy: Vol. 5, No. 4, pp. 367-370.

Direct measurement of thermal expansion of sea water under pressure

The effect of pressure on the electrical conductance of sea water

Abstract : A sea-going conductivity bridge (Salinometer) for measuring the salinity of sea water is described in considerable detail. In principle, the salinity of an unknown sample is determined by comparing its conductivity with that of a sample of known salinity at the same temperature. The calibration of the bridge is found empirically. The instrument consists of a constant temperature bath, a 1000 cycle impedance bridge using glass conductivity cells in two of its arms, a phase detector to convert the 1000 cycles output of the bridge to DC and a balancing mechanism to complete automatically the 'fine' adjustment in bridge balance. It operates from a 110 v60 cycle power source. (Author)

Karl E. Schleicher

Papers

A new high pressure equation of state for seawater

A new high pressure equation of state for seawater

Direct measurement of thermal expansion of sea water under pressure

The effect of pressure on the electrical conductance of sea water

A Conductivity Bridge for Measurement of the Salinity of Sea Water