TSG – Temperature and salinity of near-surface seawater

The thermosalinograph (TSG) measures the surface temperature and electrical conductivity of the water pumped in via the water inlet, which is a few metres deep. These parameters are used to calculate the salinity. The TSG is installed inside the ship one metre behind the water inlet, and there are currently two common types. One is the ‘SBE21 SeaCAT Thermosalinograph’ and the other is the ‘SBE45 MicroTSG Thermosalinograph’. Both devices are identical in terms of their measuring principle and function both when the ship is moving and when it is stationary. A TSG is usually connected to an additional temperature sensor, in most cases an ‘SBE38 Digital Oceanographic Thermometer’. This is installed directly at the water inlet and determines the temperature of the water being pumped past. This temperature is given as the TSG temperature, while the calculated salinity represents the TSG salinity.

Large research vessels always have two TSGs and two additional thermometers, which run either in parallel or in predefined alternating operation.
Ocean temperature and salinity are the basic hydrographic parameters used to determine, for example, the density of seawater. Precise knowledge of these parameters and their variability on different spatial and temporal scales is fundamental for determining water movements at different depths and also the exchange of energy with the atmosphere.

Michael Schlundt, a data steward based at GEOMAR with a scientific background in meteorology and physical oceanography, is responsible for processing the TSG data. The data steward’s main tasks are to monitor the general data flow of the TSGs on German research vessels, which includes both the daily data stream of values from the last 24 hours and the downstream processing, quality control and publication of data based on individual sea voyages. He is also the contact person for various questions relating to TSG data.

[SOPs | Data records]