February 18, 2024

Ocean Warrior Science #2

Ocean Warrior Science #2

Ocean Warrior - What we measure and Why #2

Salinity: Salinity levels influence the ocean's density and circulation patterns and are critical for understanding the global water cycle.

Measuring salinity in oceanography is crucial for several reasons:

Climate Regulation:

Salinity, along with temperature, helps to drive global ocean circulation patterns, which in turn play a key role in regulating theEarth's climate. These patterns are part of the thermohaline circulation, often referred to as the global conveyor belt, which distributes heat around the planet.

Marine Ecosystems:

Salinity levels affect the marine ecosystems profoundly.Many marine organisms are adapted to live within specific salinity ranges, and significant changes can impact their survival, reproduction, and distribution. 

Water Cycle:

Salinity measurements help scientists understand the Earth's water cycle. By tracking how salinity changes in different parts of the ocean, researchers can infer patterns of evaporation and precipitation as well as river discharge and ice melting.

This may be of interest and also explains why our calibration and validation data for satellites is crucial for accuracy particularly in remote areas.

Density and Buoyancy:

Salinity affects the density of seawater, which influences ocean currents and the buoyancy of marine organisms. This has implications for nutrient mixing and the vertical distribution of marine life.

Chemical Processes:

Salinity influences the rates of chemical reactions in the ocean, affecting processes like the absorption and storage of carbon dioxide.This is important for understanding the ocean's role in carbon cycling and its impact on global climate change.

Ocean Acoustics:

The speed of sound in seawater is affected by temperature, pressure, and salinity. Accurate measurements of salinity are, therefore, important for submarine navigation and underwater communication.

Research and Monitoring:

Ongoing salinity measurements are essential for monitoring changes in the ocean that may indicate broader environmental shifts, including global warming and climate change.

In essence, salinity is a fundamental measure that interconnects various physical, chemical, and biological processes in the ocean, making it a vital parameter for the field of oceanography.

So how will we measure Salinity?

The measurement of salt in the sea, or salinity, can be done through various methods:

Conductivity Sensors:

Salinity can be estimated by measuring the electrical conductivity of seawater, which increases as the salt content rises. This is one of the most common methods and is used by devices known as CTD(Conductivity, Temperature, and Depth) sensors that provide profiles of salinity throughout the water column. This is our main method.

Valeports superb SWIFT CTD that we use on our expeditions

A refractometer measures the extent to which light is bent, or refracted, when it moves from air into seawater. The bending of the light increases with the salinity of the water.


This device measures the salinity of water based on the principle that the boiling point of water increases with the amount of salt dissolved in it.

Chemical Tests:

The traditional titration method, known as argentometrictitration, uses silver nitrate to precipitate chloride ions from a sample. The amount of silver nitrate used gives an estimate of the salinity.


A hydrometer is a device that measures the specific gravity(density) of liquids. Since the density of seawater is affected by its saltcontent, this can be an indirect measure of salinity.

Satellite Remote Sensing:

Satellites can measure sea surface salinity by detecting the thermal radiation emitted from the surface of the ocean. This method provides large-scale and continuous data.

Each method has its own advantages and limitations in terms of accuracy, cost, and application range. In modern oceanography, CTD casts are commonly used for precise measurements, while satellites offer broader coverage for surface salinity.