Deployment of an Argo float from a ship.
Monitoring our oceans with robotic floats
Argo robotic floats are the only means to collect the subsurface observations needed to provide year-round, near real-time information on ocean conditions.
25 November 2005 | Updated 14 October 2011
Argo is a major international collaborative project to observe the world’s oceans and help scientists understand ocean processes and the ocean’s role in climate. The data collected also improves our ability to forecast climate and ocean conditions.
Argo consists of a global array of robotic ocean instruments. These instruments, or floats, are the only means to collect the regular subsurface observations needed to provide year-round, near real-time information on ocean conditions.
When complete in 2007 Argo will be a global array of 3 000 free-drifting robotic instruments to monitor the oceans and help scientists understand ocean processes.
The floats drift at depths of between 1 and 2 km. Every ten days each float ascends to the surface, measuring temperature and salinity as it rises. This data is transmitted to satellites along with the float’s position. The float then dives and starts a new cycle.
Australia launched the first ten Argo floats in the Indian Ocean in 1999. Today 2 100 are in place and the global target of 3 000 floats should be reached in 2007.
Australia (through the Antarctic Climate & Ecosystems Cooperative Research Centre, Wealth from Oceans Flagship and Bureau of Meteorology) has deployed nearly 120 floats in the Indian, Pacific and Southern Oceans.
Why is Argo data needed?
Argo data is used in operational ocean and climate analysis and forecasting, and oceanographic and climate research.
The oceans store and transport vast amounts of heat. Three metres of ocean has the same heat capacity as the entire atmosphere, so the ocean plays a large role in climate changes seasonally and over longer time periods.
How do the floats work?
The floats drift at depth because they are less-compressible than seawater. They rise to the surface by pumping fluid from inside the float to an external bladder, changing their volume. When it is time for the float to dive the fluid is drawn back inside, making the float denser than the surrounding seawater. Floats can be deployed from research or commercial ships and from aircraft.
Argo, Jason and other ocean observations
Argo has a close partnership with the Jason altimetry satellite. Satellite radar altimeters reveal the shape of the ocean surface over hundreds of kilometres as it is influenced by currents and by heat storage. A series of such satellites (ERS, Topex - Poseidon and now Jason and ENVISAT) have partnered profiling floats.
Argo is sponsored by the World Climate Research Programme’s Climate Variability and Predictability project (CLIVAR) and by the Global Ocean Data Assimilation Experiment (GODAE). It is a pilot project of the Global Ocean Observing System (GOOS).
See daily global float positions at the Argo International website [external link].