In-situ sea temperatures have been obtained using two Richter and Wiese protected reversing thermometers mounted on a Nansen bottle. Temperature readings, after correction according to the thermometer's calibration certificates are averaged if the temperature difference among thermometers is lower than 0.2°C and repeated otherwise, so that the accuracy can be set to be lower than 0.2°C. Thermometers are periodically controlled at facilities of the Marine Research Institute (ICM) in Barcelona against a high precision Pt100. which, in turn is annually controlled using Ga and pure H2O melting points.