Expendable Bathythermograph


The expendable bathythermograph (XBT) sub-facility collects temperature profiles of the oceans surrounding Australia using high-resolution repeat lines samples collected by merchant ships equipped with a XBT.  High-resolution temperature profiles are regularly collected along the 5 IMOS-funded sections (two of the three the Tasman Box lines, the Fremantle-Indonesia line, the line from Hobart to the French Antarctic Base –  Dumont d’Urville – and the line within the Java/Banda Sea running from west to east).  The XBT probes sample to approximately 800m and have a nominal accuracy of 0.15°C.  The depth of the temperature profile for an individual probe is determined by a fall rate equation.  These data are used in many studies to characterise the mean and time-varying properties of the major ocean currents around Australia.

Instrumentation and Data

The Expendable Bathythermograph (XBT) has been used by oceanographers for many years to obtain information on the temperature structure of the ocean to depths of up to 1800 meters. The XBT, shown in Figure 1, is a probe which is dropped from a ship and measures the temperature as it falls through the water. Two very small wires transmit the temperature data to the ship where it is recorded for later analysis. The probe is designed to fall at a constant rate, so that the depth of the probe can be inferred from the time since it was launched. By plotting temperature as a function of depth, the scientists can get a picture of the temperature profile of the water.

Useful Links


Dr Ann Thresher


CSIRO Oceans and Atmosphere Flagship

Bureau of Meteorology (BoM)

International programs:

The Global Temperature and Salinity Profile Programme (GTSPP)

International Quality controlled Ocean Database (IQuOD)

SOOP Implementation Panel (SOOPIP)


Your access to IMOS Expendable Bathythermograph (XBT) data discovery and exploration is through the  Australian Ocean Data Network (AODN) Portal.