The density–salinity relation of standard seawater

Schmidt, Hannes; Seitz, Steffen; Hassel, Egon; Wolf, H.

doi:10.5194/os-14-15-2018

Cited by 38 publications

(24 citation statements)

References 47 publications

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“…Salinity itself is a sophisticated quantity, which has been difficult to define (IOC, SCOR, and IAPSO 2010), and measuring it with high accuracy is difficult even today (Budéus 2011). Despite remaining caveats (Schmidt et al 2018;Budéus 2018), practical salinity can be determined as a unique parameter, and salinity changes can be analyzed by assessing salinity and ocean transports in a unique way, including the input of pure freshwater. It is entirely counter-productive to dilute the parameter salinity by watering it down with the artificial and ambiguous construction of "oceanic freshwater fraction".…”

Section: Resultsmentioning

confidence: 99%

“Freshwater” in the Ocean is Not a Useful Parameter in Climate Research

Schauer

Lösch

2019

Journal of Physical Oceanography

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Ocean water is freshwater with salt. The distribution of salt concentration in the ocean changes by addition and removal of freshwater in the form of precipitation, continental runoff, and evaporation, and by a flow of saline ocean water that gives rise to a salt flux divergence. Often, changes in salinity are described in terms of "freshwater content" changes and oceanic "freshwater transports", defined as fractions of freshwater. But these freshwater fractions are arbitrary, because they are defined by a non-unique reference salinity. Also all temporal and spatial comparisons and anomalies of such freshwater fractions in the ocean depend on the choice of reference salinity in a nonlinear way, because in the definition of the fraction it appears in the denominator. Consequently, any conclusion based on the comparison of freshwater fractions is ambiguous. Since there is no definite physical constraint for a unique reference salinity, freshwater fractions are declared not useful for the assessment of the state of ocean regions and the associated changes. In the light of ongoing changes in the water cycle and the global nature of climate science, scientific results need to be expressed in a way so that they can be easily compared and integrated in a global perspective. To this end, we recommend to avoid freshwater fraction as a parameter describing the ocean state. Instead, one should use the terms of the salt budget to obtain unique results for quantifying and comparing salinity.

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Section: Resultsmentioning

confidence: 99%

“Freshwater” in the Ocean is Not a Useful Parameter in Climate Research

Schauer

Lösch

2019

Journal of Physical Oceanography

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“…This accuracy permits the use of IAPWS-95 for the calibration of high-precision density meters (Wolf, 2008). By means of such instruments, seawater salinity may be determined from measured densities, and sea-salt composition anomalies may be detected Feistel et al, 2010c;Wright et al, 2011;Woosley et al, 2014;Pawlowicz et al, 2016;Schmidt et al, 2016Schmidt et al, , 2018Budéus, 2018); see also Sect. 3.4.…”

Section: Helmholtz Function Of Fluid Watermentioning

confidence: 99%

“…Although the intended new salinity definition appears physically and metrologically sound, there are a large number of detailed technical, metrological, logistical and financial questions and problems that need to be addressed before a new international, density-based salinity standard may be introduced officially Schmidt et al, 2016Schmidt et al, , 2018. Among the related research tasks of JCS is finding an explanation for unexpected systematic negative density anomalies like those displayed in Fig.…”

Section: Seawater Salinitymentioning

confidence: 99%

“…3. Here, β is the haline contraction coefficient of seawater, which has a typical value of about 0.73 at 35 g kg −1 , 1000 hPa and 300 K. As a revival of previous, so-called specific-gravity methods (Forch et al, 1902;Krüm-mel, 1907), this density-based approach relies on the high accuracy of modern vibrating-tube density meters (Kremling, 1971;Wolf, 2008;Schmidt et al, 2016Schmidt et al, , 2018. Before TEOS-10, the international standards attempted to avoid inconsistent results caused by using different methods of salinity determination.…”

Section: Salinity Scalesmentioning

confidence: 99%

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Thermodynamic properties of seawater, ice and humid air: TEOS-10, before and beyond

Feistel

2018

Ocean Sci.

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Abstract. In the terrestrial climate system, water is a key player in the form of its different ambient phases of ice, liquid and vapour, admixed with sea salt in the ocean and with dry air in the atmosphere. For proper balances of climatic energy and entropy fluxes in models and observations, a highly accurate, consistent and comprehensive thermodynamic standard framework is requisite in geophysics and climate research. The new Thermodynamic Equation of Seawater -2010 (TEOS-10) constitutes such a standard for properties of water in its various manifestations in the hydrological cycle.

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“…The equation of state (12) and its derivative forms (13) and (14) differ in that for them it is not actually necessary to impose such a serious restriction as the coincidence of the sea water ionic composition structure with the international standard [4]. Therefore, unlike the equations of state in the form (7) and (8) or (10) and (11), they can find application also in anomalous or non-typical zones where Dittmar`s law does not work. To establish the form of the functional dependence in equations (12) or (13) and (14), it is sufficient to have the results of synchronous in situ measurements of temperature, pressure, sound velocity and density.…”

Section: Theoretical Justificationmentioning

confidence: 99%

New Equations for Sea Water Density Calculation Based on Measurements of the Sound Speed

Grekov¹,

Grekov

Sychov³

2019

Mehatronika, avtomatizaciâ, upravlenie

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Density is one of the most important properties of seawater and is used in various marine research and technology. Traditionally, in the practice of oceanographic research, it is customary to consider density as a dependent parameter, which is a function of several other parameters taken as independent. Usually the following three parameters are used as the independent parameters: temperature, hydrostatic pressure and salinity. The issues of temperature and hydrostatic pressure measuring in situ are technologically well developed, while in the salinity measuring there are still unsolved problems. This is due to the fact that salinity is such a property that it is simply impossible to determine directly in situ. To eliminate the problems associated with measurements of salinity, the authors developed the special new kind equation. That equation of the new kind express the density of sea water through independent and in situ measured parameters: temperature, hydrostatic pressure and sound speed. The novelty of this approach is that using of the sound speed as the independent parameter makes it possible to exclude measurements of salinity. The authors developed two such new equations for the different cases of using. The first new equation is intended for use in technical applications and reproduces the sea water density in a wide range of the aquatic environment parameters with a root mean square deviation of 0.062 kg/m 3 . The second more precise new equation is intended for scientific applications and reproduces the sea water density in a narrower oceanographic range of parameters with a root mean square deviation of 0.0018 kg/m 3 .

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The density–salinity relation of standard seawater

Cited by 38 publications

References 47 publications

“Freshwater” in the Ocean is Not a Useful Parameter in Climate Research

“Freshwater” in the Ocean is Not a Useful Parameter in Climate Research

Thermodynamic properties of seawater, ice and humid air: TEOS-10, before and beyond

New Equations for Sea Water Density Calculation Based on Measurements of the Sound Speed

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