Frequently Asked Questions
* What is Argo?
Argo is an international project to collect information on thetemperature and salinity of the upper part of the world's oceans. Argo uses robotic floats that spend most of their life drifting belowthe ocean surface. They make temperature and salinitymeasurements when they come up to the surface and after transmitting their data to satellites, they return to depthto drift for 10 days. Currently, there are roughly 3000 floatsproducing 100,000 temperature/salinity profiles per year. Thefloats go as deep as 2000m. To learn more, visit the "About Argo"
* Why is it called Argo?
In Greek mythology, Argo was the ship in which Jason and theArgonauts set sail to search for the golden fleece. Argo floatssail the 21st century seas and Argo is teamed with a satellite called JASON-1
that measures the shape ofthe ocean surface. Data from Argo and JASON-1 together willmonitor the ocean currents, the oceans' transport of heat and freshwater around the globe and sea-level rise.
* What do the floats look like and how do they work?
The floats have a pressure case made of aluminium thatis about 1.3m long and about 20cm diameter. They weighabout 40kg. On the top is an antenna to communicate with thesatellites that fix the float's position and receive the data. Also on the top are the temperature and salinity sensors. At thebottom of the float in a protective cover is a bladder that isconnected to the inside of the float. The floats are designed sothat with the bladder empty they have the same density as seawater atthe depth at which they drift. They are also designed to be lesscompressible than sea water. This keeps them stable at depth.
The floats are put in the ocean from ships or aircraft and sinkto depth. After 10 days oil is pumped into the bladder anddrives the float to the surface. At the surface it is positionedby satellites and downloads its temperature/salinity profile. Thebladder then deflates and the float sinks back to depth to repeat thecycle. To learn more, visit the "How Argo Floats Work"
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* How are the floats powered and how long do they workfor?
The floats are powered by batteries. Many usemanganese/alkali batteries like you can buy in shops. Somefloats use higher-powered lithium batteries. The floats aredesigned to do about 140 cycles and so should last almost 4 years. The life depends on the depth to which they profile and the surfacewater density in which the float is operating. (If the surface waterhas low density, more oil must be pumped to drive the float to thesurface). To see plots on float lifetimes, go the the Argo Information Centre
* Who uses the data?
Argo data are used by weather and climate centers to helpunderstand the way the oceans affect climate. These centers areworking to improve forecasts of El Nino events and to understand otherclimate features like monsoons and global warming. Argo has nowbecome the main source of subsurface temperature and salinity from thedeep oceans. See the Uses of Argo Page
for more detailson the operational and research uses of Argo data.
* Where can you get the data and how much does it cost?
The most important thing about Argo data is that it is FREE toanyone wishing to use it. The data can be obtained from two globaldata servers, one in France
and one in theUSA
. To learn more, visit the "Argo data and how to get it"
* How accurate is the Argo data?
The temperatures in the Argo profiles are accurate to ± 0.005°C and depths are accurate to ± 5m. For salinity,there are two answers. The data delivered in real time are sometimes affected by sensor drift. For many floats this drift is small, and the uncorrected salinities are accurate to ± .01 psu. At a later stage, salinities arecorrected by expert examination, comparing older floats with newly deployed instruments and with ship-based data. Following this delayed-mode correction, salinity errors are reduced further and in most cases the data become goodenough to detect subtle ocean change.
* How much does the project cost and who pays?
Each float costs about $15,000 USD and this cost about doubles whenthe cost of handling the data and running the project is taken intoaccount. The array has roughly 3000 floats and tomaintain the array, 800 floats will need to be deployed each year. Thus the approximate cost of the project is 800 x $30,000 = $24m peryear. That makes the cost of each profile around $200. 28 countries have contributed floats to the array withthe USA providing about half the floats.
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* When will the Argo array be complete?
The Argo array reached 3000 floats in November 2007, and can be maintained at that level as long as nationalcommitments provide about 800 floats per year. The need for global Argo observations will continue indefinitely, though the technologies and design of the array will evolve as better instruments are built, models are improved and more is learned about ocean variability.
* How is Argo managed?
Argo has an international Steering Team and a Data Management Team made up of scientists from countries involved in Argo.An Argo Technical Coordinator monitors the array and registers each float deployment in accordance with internationalagreements. Argo also has also had an international Director, but there is currently not enough funding for this position. Each country finds its own funding and sets its own priorities for where floats are deployed in consultation with other countries.To learn more, visit the "Argo Project Office"
* What happens when floats stop working?
Most floats will "die" when the battery is tooweak to pump the float to the surface. Thesefloats will drift around in the deep ocean untilthe pressure case corrodes and the float falls tothe sea bed. However a small number will washup on the beach or, vary rarely, be caught innets. Floats have labels (in many languages) on them telling thefinder, what to do with thefloat.
* Do the floats pose any hazard to people, wildlife, the environment or shipping?
The floats make no noise in the ocean and they do notcontain materials that are not found elsewhere in the oceans. We take care to ensure that they are handled properly if they arefound by fishermen or beachcombers. They are small and lightenough to pose no significant hazad to ships and boats.
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* What should I do if I find a float?
In the rare case that a float is found on a beachwe can learn a great deal from it about why itfailed. First look for the float'sidentification. The float should have a label(shown here at right)with instructions in many languages.
If you can safely do so, move the float to alocation where it can be stored without gettingtoo hot and where it cannot be interfered with byother people.
Follow the instructions on the label and informthe Argo Information Centre in France (by email@example.com, Fax +33 5 61 75 10 14or telephone +33 5 61 39 47 30) givinginformation on the float identification numbers,where and when the float was found and where itis stored. If this is not possible please askthe local police or coast guard to contact Argo. Arrangements will then be made to return thefloat to its owner.
* Does Argo have a blog?
Yes, Argo has a blog at http://argo3000.blogspot.com/
. The blog is used to discuss issues like warming of the ocean, climate,etc. Check out the blog and add your own thoughts.