Introducing the T-Stick: A new device for high precision in situ sediment temperature profile measurements

Tomas Feseker, Gero Wetzel, Bernd Heesemann

Limnol. Oceanogr. Methods 10:31-40 (2012) | DOI: 10.4319/lom.2012.10.31

ABSTRACT: In situ sediment temperature profile measurements provide valuable information on fluid seepage, hydrate stability, and ambient temperature of samples. We present a new instrument that can be used to obtain precisely positioned sediment temperature profile measurements during ROV dives. Consisting of a sensor rod equipped with eight temperature sensors and a standard data logger, the new T-Stick can be operated by an ROV in a fully autonomous mode. The temperature range of the instrument is -5°C to 35°C, and it can withstand pressures of up to 600 bar. Virtual measurements generated by a numerical model showed that the T-Stick provides highly accurate temperature profile measurements with a root mean square error of 0.0027 K for a wide range of thermal sediment properties. Modeled temperature gradients are representative of both normal deep sea settings and cold seep environments with elevated temperature gradients of up to three orders of magnitude above normal background values, which are the primary target areas for T-Stick measurements. Deviations from the true in situ temperature profiles are caused by disturbance of the temperature field by the probe itself and may lead to underestimation of gradients and curvature in the profiles. A first field test of the T-Stick at 1250 m water depth demonstrated the usefulness of the new instrument.