Sound velocity wet test to determine ocean temperature

By: Simone Burzacott-Gorman

Every four hours the hydrographers aboard Investigator stop the ship along one of the transect lines to undertake a ‘Sound Velocity Wet Test’ (SVT) to determine ocean temperature. Instrumentation dropped on a winched line, remotely feeds ocean temperature data back to the ships coms room. Researchers then create graphs of the data. Where the graph plateaus it indicates the thermocline. The denser the water the faster the longitudinal waves travel, as sound waves are propagated by a medium, in this case colder water has greater density. Thus, changes in wave velocity are indicative of temperature. This data has a range of applications. In the northern hemisphere determination of thermocline is particularly important for sea birds as they will not dive past the change in temperature. Eric Woehler, Principal Sea Bird Investigator aboard Investigator is interested in understanding the correlation between albatross behaviour and oceanographic data like SVT.