Speed of sound measurements in North Atlantic Seawater and IAPSO Standard Seawater up to 70MPa

In this work, IAPSO (International Association for the Physical Sciences of the Oceans) Standard Seawater has been characterized by measuring the speed of sound in the temperature range of (273.15 and 313.15) K and in the absolute salinity range of (10.036 and 38.201) g·kg-1, for pressures up to 70MPa. Measurements are traceable to ITS-90 temperature, pressure and salinity reference standards. The experimental apparatus was also adapted to measure the speed of sound (SoS) in North Atlantic Seawater in the same temperature range at atmospheric pressure. These results are compared with those measured using four different commercial oceanographic sensors. The results in North Atlantic Seawater showed that, at least at atmospheric pressure, measurements with a typical uncertainty of 0.04% can be obtained if the sensors are previously calibrated with pure water in the same speed of sound range where they will be utilized during oceanographic cruises. In the case of North Atlantic Seawater at atmospheric pressure, when experimental results are compared with those predicted by TEOS-10 equation of state, the agreement is generally better than 0.03%. At higher pressures, speed of sound results, measured in IAPSO Standard Seawater, show an agreement on the order of 0.06% with the exception of the sample with absolute salinity equal to 10.036g·kg-1. •Speed of sound measure in North Atlantic and IAPSO Standard Seawater up to 70MPa•Speed of sound (SoS) measurements were carried out in far-field conditions.•SoS results in North Atlantic seawater were obtained by two different techniques.•Obtained resuts were compared with those predicted by TEOS-10 equation of states.