Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


New equation of state of seawater

Proposed new international 'equation of state' employs absolute over practical salinity to redefine thermodynamic equation of seawater after 30 years

Seawater is a complex, dynamic mixture of dissolved minerals, salts, and organic materials that despite scientists best efforts, presents difficulties in measuring its potential to contain and disperse energy. Like the water itself, the calculations scientists employ to measure seawater are fluid, undergoing significant revisions and clarifications over the years as research techniques and instrumentation continues to evolve.

For 30 years, scientists have relied on a series of equations called International Equation of State of Seawater – or EOS-80, a collective term representing more than three decades of oceanographic best practice information from the early 1980's to present. Now, based on new oceanographic research, scientists have begun adopting a fresh approach to seawater thermodynamics, based in part by the work of University of Miami (UM) researcher, Dr. Frank Millero. Referred to collectively as the "Thermodynamic Equation Of Seawater – 2010," or "TEOS-10" for short, a new set of highly accurate and comprehensive formulas are beginning to provide much-needed adjustments and clarifications to the widely used EOS-80, that may be accepted internationally as early as 2010.

A member of the original committee that established the EOS-80, and a major contributor to and publisher of its latest revisions, UM Rosenstiel School of Marine and Atmospheric Science Professor Millero, is a leading force in oceanic chemistry research. His work alongside scientists from the across the United States, Canada, Europe, Great Britain, Australia and China is helping to guide the comprehensive reevaluation and construction of a set of equations that may well usher in sweeping advancements in the fields of marine and atmospheric science.

The Practical Salinity Scale, or PSS-78, and the previous International Equation of State of Seawater, which expresses the density of seawater as a function of Practical Salinity, temperature and pressure, have served the oceanographic community well for three decades, along with a number of other equations formed to incorporate more accurate representations of seawater measurements and algorithms.

"With the advancements in high speed computer processing, and progress in other scientific disciplines, the need for a new equation of state was imminent," said Millero. "These developments, along with scientific demand for more accurate equations and the emphasis on the ocean as an integral part of the global heat engine, have lent weight to a series of recently published papers utilizing increasingly precise formulas that we are hoping will be adopted universally within the next year or so."

The new equation of state is a free energy function that can yield all the thermodynamic values of seawater of known temperature, salinity and pressure. This is more convenient than EOS-80 for modelers who examine the theoretical properties of seawater. Dr. Rainer Reistel, from the Leibniz Institute for Baltic Sea Research in Germany, is widely recognized as the pioneer in developing the new free energy function.

In 2005, the Scientific Committee on Oceanic Research (SCOR) and the International Association of Physical Sciences of the Ocean (IAPSO) established Working Group 127 on the "Thermodynamics and Equation of State of Seawater," or simply WG127. Since then this group has arrived at a series of algorithms that incorporate oceanography's best knowledge of seawater thermodynamics. The approach taken by WG127 has been to develop a Gibbs function from which all the thermodynamic properties of seawater can be derived by purely mathematical manipulations. This method ensures that the various thermodynamic properties are self-consistent and complete. Named for physical chemist G. N. Gibbs, who developed free energy equations that can be used to study the thermodynamic properties of fluids. The new equation of state is based on a Gibbs function for seawater from which all the thermophysical properties of seawater can be derived in a physically consistent manner.

"The Gibbs function is a function of Absolute Salinity, temperature and pressure, which is a major departure from present practice (EOS-80). The reason for preferring Absolute Salinity over Practical Salinity is because the thermodynamic properties of seawater are directly influenced by the mass of dissolved constituents, or Absolute Salinity, whereas Practical Salinity depends of conductivity," said Millero. "If the new approach to defining the thermodynamic properties of seawater is well received by the scientific community, we would hope that TEOS-10 will become the new internationally accepted definition of seawater by 2010."

While Practical Salinity will still be the salinity variable that is stored in national databases (much as in situ temperature is stored in these databases), it is the new Absolute Salinity that will be used in journal publications, numerical ocean models and inverse models (as temperature is not used now, but rather, potential temperature for these purposes). The main reason for adopting the new salinity variable is to allow for the spatial differences in seawater composition; this variable composition affects conductivity differently to how it affects factors such as density, enthalpy, entropy and more.

Barbra Gonzalez | EurekAlert!
Further information:

More articles from Earth Sciences:

nachricht UCI and NASA document accelerated glacier melting in West Antarctica
26.10.2016 | University of California - Irvine

nachricht Ice shelf vibrations cause unusual waves in Antarctic atmosphere
25.10.2016 | American Geophysical Union

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

How nanoscience will improve our health and lives in the coming years

27.10.2016 | Materials Sciences

OU-led team discovers rare, newborn tri-star system using ALMA

27.10.2016 | Physics and Astronomy

'Neighbor maps' reveal the genome's 3-D shape

27.10.2016 | Life Sciences

More VideoLinks >>>