Redefinition of Seawater to Aid Climate Research

Hydro International -

Dr Trevor McDougall, specialist in thermal fluid dynamics, CSIRO Wealth from Ocean Flagship, recently led an international science team which has released a new thermodynamic definition of salinity, ‘heat content' and other seawater properties. The science behind understanding the movement of heat through the world's deep oceans is entering a more exact phase with the adoption of a new thermodynamic definition of what constitutes "seawater".

Seawater is a mixture of 96.5 per cent pure water and 3.5 per cent other material, such as salts, dissolved gases organic substances and un-dissolved particles. Salinity, comprising the salts washed from rocks, has been deduced to date solely using the conductivity of seawater.

The new definition of seawater builds on this observational approach and additionally allows for the spatially variable composition of seawater which is not apparent in the conductivity measurements alone.

Speaking at the International Union of Geodesy and Geophysics (IUGG) conference in Melbourne as this year's Prince Albert I Medal winner, Dr McDougall said the new definition facilitates the more accurate representation of heat content and of heat uptake by the ocean. The Prince Albert I Medal has been awarded to Dr McDougall for his fundamental advances in ocean mixing processes.

"To date the ocean's role in the climate system has been handled only in an approximate manner, both because of a lack of theoretical understanding of the "heat content" of seawater, and also because of the inability to calculate the required thermodynamic quantities.

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