Profiling floats - Argo


Brief history: 

Profiling floats are autonomous ocean robots, part of the international Argo program - a major component of the Global Ocean Observing System (GOOS). The level of Argo international collaboration is unprecedented in the oceanographic community, about 30 nations are currently involved in this international observing effort. The first Argo floats was deployed in the 2000s and deployments continue today at a rate of 800 to 1000 per year. Today, the Argo network counts almost 4,000 operational floats deployed in the global ocean. See Argo story map


Description & functioning:

Argo floats are deployed by sailors or scientists during campaigns at sea. After the deployment, the float descends to a target depth of 1000m to drift freely with the currents, then it descends again to the final chosen depth (generally 2,000m). Once reached this chosen depth, the float goes up till the surface measuring a “profile” of temperature, salinity and pressure. The full "cycle" is about 10 days. Each float dives vertically by inflating or deflating an external bladder to change its buoyancy.

When the float reaches the surface, thanks to the antenna on the top of its head, it transmits all the collected data to satellites. Finally, Argo data is made available within 24 hours to scientists around the world.

After about 200 missions – around 5 years –  the batteries are exhausted, and with no energy to bring it to the surface, the float drifts and finally sinks to the sea floor, unless recovered.


In the last few years, Argo teams have developed 2 more sophisticated Argo floats, the Deep float which can dive to depth of 4,000 - 6,000m to better understand important ocean changes like increasing ocean heat content, and the Biogeochemical float equipped with sensors to investigate the processes controlling biological and chemical cycles in the ocean.

Deployment location

Argo floats are generally deployed in the open ocean.

Data collected:

All floats measure temperature, conductivity (from which we can deduct salinity) and pressure from the sea surface to 2,000m, 4,000m or 6,000m depth.

BGC floats are equipped with additional sensors to measure:

  • Oxygen
  • Nitrate
  • pH
  • Chlorophyll
  • Etc.
 Societal applications:

Ocean data measured by Argo floats are used by scientists worldwide for climate studies and to monitor ocean and ecosystems health, as well as by operational weather forecasting centers to improve weather forecast and climate predictions. Some of the Argo data applications are:

  •  Study and predict climate change
  • Monitor the ocean circulation and its changes
  • Predict hurricanes, cyclones, storms, etc.
  • Monitor ocean health
  • Etc.


  If you want to learn more about this program, visit the website: