Within the scope of climate research, researchers measure several important properties of the world's oceans, two of which are salinity and pH. Climate change is changing the density and salinity of seawater. As a result, the major ocean currents (such as the Gulf Stream) which have a major impact on the climate themselves may change (albeit very slowly). For this reason, measurement results must be comparable over long periods of time and must have measurement uncertainties that are as small as possible. Within the framework of a European research project, PTB has implemented the traceability of salinity measurements to the SI system with suitable measurement uncertainties.

In a joint project with the Leibniz Institute for Baltic Sea Research in Warnemünde, PTB has, for the first time, made optical measuring methods (which are most frequently used in oceanography) traceable to the metrologically sound, electrochemically measured pH value. This will make it possible to measure the pH values in oceans in such a way that they are comparable in the future, which is of particular interest for quantifying the acidification of the oceans caused by anthropogenic CO2. This acidification influences the diversity of marine microbes and coral growth. PTB is planning to further expand its primary measuring stations in the future, e.g. for applications at high pressure as is prevalent in great ocean depths.

Participating department
3.1 General and Inorganic Chemistry