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What is an Argo Float?

Argo Floats are robots that float at different depths in the sea collecting information. Every 10 days they float to the surface and send their data to a satellite.

An Argo Float is a steel float weighing about 25kg, with instruments inside. An Argo float is able to do three things:

An Argo Float:

  1. is able to change its buoyancy so it floats at different depths
  2. is able to take measurements of sea water
  3. is able to send information to a satellite.

Argo Float buoyancy

By changing its own buoyancy, an Argo Float is able to float at different depths. Every 10 days the Argo Float returns to the surface to send information to satellites. This information is called a 'profile'.

How do Argo Floats measure the ocean?

A fun and quirky YouTube video animationExternal Link that explains what an Argo float is, how it operates and how the data helps us understand ocean circulation and climate.

(Story by Malou Zuidema and Esmee van Wijk, Artist Malou Zuidema, Scientist Esmee van Wijk, Voice-over Jan Zika. Thanks to Australia Argo Team, Supported by CSIROArgoExternal Link and IMOSExternal Link.)

Argo measurements

While the Argo Float is underwater it measures three things about the ocean:

An Argo Float measures:

  1. salinity (amount of salt in the water) measures in parts per thousand
  2. temperature in degrees Centigrade (°C)
  3. pressure in decibars (db)

Note that 1decibar (db) of pressure is equal to about 1 metre of depth. So 1,000db is about 1,000m below the sea surface. 

Argo information to satellites

While the Argo Float is on the sea surface it sends its information to a satellite. 

  1. temperature and depth
  2. salinity and depth
  3. position 

Regular Argo Floats

Regular Argo Floats are designed to be strong enough to descend to 2,000m below the surface of the sea.  At a depth below 2,600m they will crush and be destroyed.

Deep Argo Floats

Deep Argo Floats are designed to go down to depths as far as 5,000m. Deep Argo floats are glass spheres not metal cylinders. 

A regular argo float is a steel cylinder about 2m high. It contains a battery, a buoyancy device, measuring equipment and a satellite antenna. Image source 


An Argo Float ready for deployment.


An Argo Float being deployed over the side of a ship.

Next step learning: What do you think scientists would like to know about the ocean.