Dr Mike Williams from NIWA explains how the density of the seawater is measured, by looking at the conductivity and temperature of the water.
DR MIKE WILLIAMS
To measure the saltiness in the water we essentially measure its conductivity and its temperature. And the conductivity is the rate at which we can pass electricity through a small sample of sea water. So that gives us a nice easy way to measure it. We just lower an instrument through the water, it measures the conductivity, it measures the temperature, that allows us to calculate the salinity. And we have a nice container that we have a hole in the floor of, and we work through that, lowering our instruments to the sea floor.