“The changes are important because variations of salinity and temperature are responsible for driving deep ocean currents and the major vertical overturning circulations of the world’s oceans,” says Dr Trevor McDougall, of CSIRO's Wealth from Oceans Flagship. “Getting these circulations right is central to the task of quantifying the ocean’s role in climate change.”

“We feel we are sufficiently well-advanced with our arguments to now go out to the oceanographic community and propose adoption of new and more accurate oceanographic variables that we suggest be called ‘Absolute Salinity’, and ‘Conservative Temperature’.” These more accurate variables will take the place of today’s Practical Salinity and Potential Temperature.

r Trevor McDougall (left) who leads the project defining 'seawater', and research project colleague Dr David Jackett.

He says the new description of seawater is the result of many years of research into ocean energy and the properties of seawater. This work was mainly done in Germany (Dr Rainer Feistel), the US (Dr Frank Millero) and Australia.

Dr McDougall said the new definition allows, for the first time, an accurate measure of the heat content of seawater for inclusion in ocean models and climate projections.