Which instruments are commonly used to measure ocean salinity?

CTD sensors and salinometers are specifically designed to measure water properties in the ocean, including salinity. CTD stands for Conductivity, Temperature, and Depth, and these instruments provide precise readings of how conductive the water is, which directly correlates to salinity levels. As seawater's conductivity increases with higher salinity, scientists can infer salinity from these measurements.

Salinometers are specialized devices that directly measure the salt concentration in seawater. They can either give absolute salinity readings or be part of a system that integrates data from other measurements to provide a comprehensive profile of the ocean's salinity across different depths and locations.

In contrast, thermometers measure temperature, which, while important in oceanographic studies, does not provide salinity data. Sonar devices are primarily used for mapping the seafloor or measuring the distance to objects underwater, while GPS technology helps in positioning and navigation but does not measure oceanic properties like salinity. Thus, the use of CTD sensors and salinometers is fundamental in assessing ocean salinity accurately, making them the correct instruments for this purpose.