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Photo or Argo float deployment

How We Observe the Ocean

Argo Profiling Floats

Argo, named after a mythological Greek ship, is an international collaborative ocean-observing program of over 3,500 drifting floats that gather approximately 120,000 temperature, salinity and depth profiles throughout the world’s oceans every year.  Combined with satellite observations, the information gathered by Argo floats allows ocean scientists and the public at large to better understand ocean dynamics and forecast global climate.  Over fifty nations worldwide participate in the program.   The U.S. component is implemented by NOAA.

Argo provides the first ever global-scale, all-weather subsurface observations of the ocean.  The Argo float network has played a key role in our understanding of ocean dynamics, ocean warming, and represents a major step forward in the ability to monitor ocean chemistry (e.g., dissolved oxygen, ocean acidity [pH]) globally, at higher frequency and lower cost than previously possible.

  • Argo Array
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Deployment of the Argo array began in 2000, and reached 100% of its initial design goal of 3,000 floats in 2007. Because the typical lifetime of an Argo float is 4-5 years, maintaining the array requires replacement of about 800 floats per year.  It is now recognized, however, that additional floats are needed, because high latitude areas of the ocean require a higher density of floats to adequately characterize the state of the ocean.  The measurements from the Argo array have demonstrated the need for climate observations below 2000 meters in depth in order to measure the total global heat storage in the ocean; designing and building deep diving floats is a critical technology challenge, as is expanding measurements to better sample the marginal seas and rapidly flowing boundary currents.

Photos of research scientist holding an Argo float, and Argo float bobbing in water.

Dana Swift (Left), University of Washington, holds an Argo Float, an autonomous, free-floating ocean device that collects vertically-resolved data, including temperature, to a depth of over 6000 feet, surfacing every 10 days to transmit data (Right) for over four years without servicing. Each instrument weighs approximately 65 pounds.

The bright yellow floats drift on ocean currents descending to depths of over 6000 feet. After about 9 days submerged each float rises to the surface collecting temperature, salinity, and other data that are transmitted via satellite when the float reaches the surface.  

Schematic of Argo functionality in ocean

Schematic of a profiling float cycle. Upon reaching the surface at the end of a cycle, the data obtained are transmitted via satellite with most of the data being available to operational centers and researchers within twenty-four hours of collection.

Argo data are also being used in an ever-widening range of research applications that have led to new insights into how the ocean and atmosphere interact in extreme as well as normal conditions over periods ranging from days to decades. For example, Argo data help identify the mechanism in polar winters whereby the deep waters that fill most of the ocean basins are formed and, at the other temperature extreme, the transfer of heat and water to the atmosphere beneath tropical cyclones. Both of these phenomena, which are crucial to global weather and climate, could not be observed by ships.

Working with multiple partners the U.S. Argo Program provides and deploys approximately half of the floats in the global Argo array, and carries out data communications and data management for those floats. U.S. Argo contributes to ongoing float technology develop¬ment, and has roles in the international coordina¬tion of Argo. The U.S. Argo Program is funded by NOAA and is implemented by a partnership of five institutions: Scripps Institution of Oceanography (UCSD), the University of Washington, Woods Hole Oceanographic Institution, NOAA's Pacific Marine Environmental Laboratory, and NOAA's Atlantic Oceanographic and Meteorological Laboratory. The U.S. Navy is also a partner, providing public internet access to Argo data via one of Argo's Global Data Assembly Centers.

Argo data are publically available in near real-time via the Global Data Assembly Centers (GDACs) in Brest, France and Monterey, California after an automated quality control (QC), and in scientifically quality controlled form, delayed mode data, via the GDACs within six months of collection.

Schematic of Argo functionality in ocean


International contributions to the global array of Argo profiling floats as of 31 December 2012.