How Do Oceanographers Measure Salinity?

Reasons for Salinity Testing

• Because salinity measurements aid in the understanding of ocean circulation and currents, the information gathered is used to understand the ocean's influence on global weather patterns. Salinity measurements are used to test the reversal of the North Atlantic Deep Flow, which is a change in the southerly flow of cold water from the North Atlantic, which normally travels at depth. Salinity is also measured for sonar equipment effectiveness, as salinity is a key factor in ocean sound travel.

Testing Process

• Traditionally, ocean salinity was measured by the amount of salt found in 1,000 grams of water. Although salinity amounts vary, depending on the ocean, the average ocean salinity is 35 parts per thousand. However, since the introduction of the Practical Salinity Scale in 1978, ocean salinity is now measured in laboratories by salinometers, which determine the electrical conductivity of the water sample.

Salinometers

• The salinometer is the primary instrument used by oceanographers to measure ocean salinity. First developed by Tim Dauphinee in 1975, salinometers consist of a four electrode cell in a temperature-controlled bath, measuring the samples conductivity. Industry standard salinometers include the Autosal and Portosal units manufactured by Guildline Instruments LTD. These salinometers achieve accuracy within -0.002 Practical Salinity.

Future Salinity Tests

• The future of ocean salinity testing may be space based. The Aquarius satellite, launched in 2010, is NASA's first attempt to measure ocean salinity from space. Aquarius has the ability to track salinity in remote ocean areas with a passive salinity sensor L-band radiometer.