Water Column

The water column extends from the top of the surface to the bottom of the floor. When studying the ocean, the depth of the water column can be a great as 11km! That is even taller than Mount Everest - the highest point on Earth. Scientists describe the water column by dividing it into layers that have certain features.

Exploring the water column is achieved through a range of techniques, depending on the particular interests of scientists.  Those studying marine life may be interested in the food chain or how food and chemicals move through the water layers.  Others might investigate the differences in water composition, its temperature and movement.  Understanding the water that makes up this environment can be done in many ways using a wide range of instruments.



Profiling of the water column is taking a suite of measurements and comparing them against the depth at which the measurement was taken.  An instrument package is vertically lowered through the water and then returned to the surface.  This gives one profile, or vertical line of data, through the water column of one point or ‘station’ on the oceans surface.  Scientific cruises often take a series of profiles along a line on the ocean surface, which can be joined together to form what is called a section.  A section is a two-dimensional plane of data or ‘picture’ through the water column.  If a section across an ocean starts and ends close to the coast, then the section is bounded and additional information on the physics of the ocean can be inferred.  With many international programmes in operation, there are a large number of sections available to researchers.

  • Conductivity Temperature Depth

    A large instrument package called a CTD is the standard workhorse of oceanographers for acquiring water column profiles. It is called a CTD because as a minimum it measures electrical Conductivity, Temperature, and Depth (pressure). Read more about the CTD

  • Microstructure Profiling

    One disadvantage of the CTD is the ship rolling motion in the waves causes the CTD package to move up and down continuously. As a CTD is quite large, its drag and entrainment of water creates a lot of mixing of fine-scale structure in the water around it and prevents making small scale measurements.  Read more about microstructure profiling

  • Towed Undulators

    The main problem with CTDs and Turbulence profilers is the time taken to gain one profile thus the number of profiles (usually 50-100 per month), and hence resolution that can be obtained in one section. If high spatial resolution data is required, we can profile whilst the ship is underway using a Towed Undulator. Read more about towed undulators


    BRIDGET is a towed vehicle used for chemical and biochemical analysis of seawater down to depths of 5000m. Designed to be as flexible as possible, BRIDGET has a standard suite of instruments for sampling and measuring the plumes from underwater volcanic vents, “Black Smokers”. Read more about BRIDGET

  • Acoustic Doppler Current Profilers

    Acoustic Doppler Current Profilers (ADCPs) are type of sonar (SOund Navigation And Ranging) device. They can be fitted either to the hull of a vessel and look down through the water column, fitted to CTDs or other sensors that are lowered down through the water column, or fitted to landers or moorings that sit on the sea bed and look upwards. Read more about ADCP

  • Gliders

    Underwater gliders are a type of robotic underwater vehicle that uses an engine to change the buoyancy of the vehicle rather than drive a conventional propeller as in our Autosub family of vehicles. Read more about underwater gliders

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