The science of climate dynamics and climate change is one of the most pressing issues of our century. To understand and predict these changes requires data sets of the highest quality. However, historical data for the ocean were collected mostly for regional objectives and were restricted to the tracks of research vessels and commercial ships. Ship observations were also weather and ice dependent, which has resulted in more observations during summer than winter. Advanced instruments and skilled technical personnel are also needed to acquire high quality data. Collecting oceanographic data of high quality are thus both time and effort consuming. The need for systematic and near real time monitoring of the ocean climate resulted in an increased attempt to take advantage of new technology, which resulted in the development of autonomous profiling floats.
Autonomous profiling floats - Argo floats
Profiling float technology makes it possible to obtain high-quality data anywhere at any time without a ship present. Argo floats are autonomous drifters equipped with sensors to record vertical profiles of temperature, conductivity and pressure and in certain cases even more parameters like oxygen and fluorescence (Gould, 2005). Floats are passive drifters in the horizontal, but they can adjust their buoyancy to control their vertical movements. Most of the time the floats stay at a parking depth, that is set prior to their deployment, but every 10th day they ascents to the surface while taking measurements. At surface, data are sent to land via satellites before the floats descend back to the parking depth.
To combat the spatial and temporal lack of data, an innovative step was taken by scientists, in 1999, to greatly improve the collection of observations inside the ocean through increased sampling of old and new quantities and increased coverage in terms of time and area. That step was Argo.
Argo is designed to observe large-scale subsurface ocean variability globally (Roemmich et al., 1999) with an array of autonomous profiling floats in the ocean. Originally, the array was 3ox3ox10-day spacing between 60oS and 60oN. The combination of the array’s high-quality temperature and salinity sensors and its comprehensive data management system produces climate-quality data, with new techniques being developed to identify and minimize systematic errors.
Deployment of Argo profiling floats began in 2000. In November 2007, the international Argo programme (http://www.argo.ucsd.edu), endorsed by the Intergovernmental Oceanographic commission of UNESCO, reached its initial target of 3,000 profiling floats. Today, the Argo array consists of more than 3,000 floats. These floats measure temperature and salinity throughout the deep global oceans, down to 2,000 metres, and deliver data both in real time for operational users and after careful scientific quality control for climate change research and monitoring. Argo is the first-ever global, in-situ ocean-observing network in the history of oceanography, providing an essential complement to satellite systems.
Active Argo floats – by country
The name Argo
The name Argo has its origin from greek mythology. Jason, a king- son from Iolkos in Thessalia, used the ship Argo on the search for the golden fleece. The crew onboard was called Argonauts, and they had many adventures. Thus, the Argo floats sails in the 21st century seas. The most important partner to the Argo project is the Jason project where the sea surface level is measured from the Jason satellite. By combining the data from Argo and Jason one can measure the ocean currents, oceanic heat and salt transports, and sea level rise.