A BRIEF HISTORY OF ARGO
In Greek mythology, Jason sailed the oceans on his ship, the Argo, in search of the treasure of the Golden Fleece.
In the 21st century a fleet of about 3000 modern-day 'Argos' is searching for an even more important treasure...
...an understanding of how the oceans affect our lives and particularly how they influence the Earth's climate!
Those modern 'Argos' are actually very clever and sophisticated robotic instruments. For reasons that will be explained we call them Argo float...
Until the middle of the 20th century, there was no method to measure currents below the surface of the open ocean.
The problem was solved in 1955 when a British oceanographer, John Swallow, developed what became known as the neutrally buoyant (or Swallow) float.
The Swallow float would stay at a fixed depth and move with the currents at that depth. The path taken by the float, and hence the current speed and direction, could be measured by scientists on a nearby ship listening to sounds ('pings') emitted at regular intervals from the float. Information from Swallow floats soon revealed that the deep oceans were not the tranquil regions predicted from theory. Instead they were filled with energetic currents that vary on scales of weeks and hundreds of kilometres, much as the atmosphere is filled with weather systems that change the speed and direction of the winds.
In the USA, Henry Stommel imagined locating his freely drifting floats a single time using the time of arrival of explosive sound waves at three shore-based SOFAR (Sound Fixing And Ranging) stations.
Independently but at the same time, in the UK, John Swallow introduced the Swallow float, inspired by Stommel’s vision of Lagrangian measurements of currents.
The Swallow float was the first passively ballasted drifter which made the first measurements of deep currents.
Rossby and Webb developed the SOFAR floats in the USA
Former SOFAR floats were converted by Tom Rossby and colleagues into moored sound sources and replaced by low-cost and lightweight RAFOS floats with acoustical receivers.
Doug Webb and Russ Davis in the USA developed the Lagrangian Ocean Circulation Explorer (ALACE).
Later in WOCE, the ALACEs were modified to measure temperature and then salinity profiles each time they surfaced. It was this technology that allowed Argo to be planned.
In France, Ollitrault et al. developed a hybrid of RAFOS and ALACE technology called MARVOR float.
A global array of 3000 profiling floats similar to the Profiling ALACE (PALACE) was proposed to the OceanObs'99 conference.
Toward the end of WOCE, the more modeller autonomous floats such as SOLO (Davis et al., 2000) and APEX correspond exactly to the category of "submarine" floats.
The first Argo floats were deployed inspired by the Greek myth of Jason and the Argonauts,
the floats were given the name ARGO to stress the way they would work with the new JASON satellite altimeter, launched in December 2001.
WHAT ARE ARGO FLOATS ?
Argo floats are drifting cylindrical containers with instruments to measure the properties of sea water.
The floats drift freely with the currents, measuring the temperature and salinity of the upper 2000 m of the ocean.
They make it possible to monitor the temperature, salinity, and current velocity of the upper ocean continuously and receive the data within hours. Some floats also make other measurements.
The body of an Argo float is made of aluminium tubing.It contains electronics, pumps and many batteries.
At the top are the sensors that measure temperature and salinity, and an antenna to transmit the data.
At the bottom is a rubber bladder, which controls the depth of the float.
Soon after a float is launched, it sinks to 1000m depth and then to 2000m, making measurements all the way.
After 10 days it returns to the surface and transmits its measurements back via satellites. The measurements are available to scientists - and to you - on the Internet.
AN INTERNATIONAL COOPERATION
More than 30 countries are directly involved in setting up the network. Since November 2007 there have been close to 4000 floats operating and delivering their measurements every 10 days.
The array is made up of 30 different countries' contributions that range from a single float, to the US contribution which is roughly 50% of the global array!
Each year, 800 to 900 new floats are deployed, the number needed to maintain a network of close to 4000 active floats given their average lifespan of 3-4 years.
12 EUROPEAN ARGO PROGRAMMES
The national Argo programmes below are all members of Euro-Argo:
The Argo programme in France is undertaken by the Coriolis partnership between the seven French institutes involved in oceanography (CNES, CNRS, Ifremer, IPEV, IRD, Météo-France, Shom).
French Argo is active in the international Argo Steering Team and the Argo Data Management Team.
Since 2000, about 450 French floats have been deployed in a number of different geographic areas.
The interests of France are global but with special interests in the Atlantic, Indian and Southern Oceans
The UK's contribution to Argo is undertaken by a partnership involving the Met Office (which manages the project),
the National Oceanography Centre, Southampton (NOC), the British Oceanographic Data Centre (BODC) and the UK Hydrographic Office (UKHO).
Since 2001, over 250 UK floats have been deployed in a range of geographic areas.
The geographical areas of UK interest are the Norwegian Sea, North and South Atlantic, South Indian Ocean, Arabian Sea and Southern Ocean.
The BODC acts as the data centre for UK Argo, and has established a delayed mode regional data centre for the Southern Ocean.
The German Argo programme is undertaken by the Bundesamt für Seeschifffahrt und Hydrographie (BSH) and the Konsortium Deutsche Meeresforschung (KDM)
with its partner institutions (AWI, IFM-GEOMAR, ZMAW).
The BSH takes the overall lead to transform German Argo into an operational system while the KDM-partners are involved in new developments and scientific applications.
Since 2000, several hundred German floats have been deployed in different geographic areas, where deployments have focused on meeting the scientific interests of the German partner institutes.
German Argo interests are mainly in the Atlantic, bug contributes to the global array in the Nordic seas and the Southern, Indian, and Pacific Oceans.
The Dutch Argo programme is carried out by KNMI, the Dutch national weather service, as part of their climate monitoring activities.
Float deployment is coordinated with NIOZ, the Netherlands Institute for Sea Research.
Float deployment started in 2004 with 4 floats. Since then several other floats have been deployedwith a focus is on optimally filling gaps in the global array of Argo floats.
The Irish Argo programme is managed by the Marine Institute (MI).
The first four floats were deployed in spring 2008 in the Rockall Trough west of Ireland.
The MI runs the Rutgers Ocean Model (ROMS) on an operational basis.
Argo profiles will provide a near real time check on model output profiles of temperature and salinity. Ireland's interests are primarily in the North East Atlantic.
In 2006 the Hellenic Centre for Marine Research (HCMR) has deployed 4 floats in the Aegean Sea, in collaboration with the University of Athens and the University of Washington.
HCMR operates the Hellenic National Oceanographic Data Centre (HNODC), and may develop delayed-mode data processing for ARGO profiles collected within the Eastern Mediterranean.
Med-Argo data are routinely assimilated on a weekly basis in one of the operational forecasting systems,
and are also used by a small group of researchers in Greece for studies of water mass characteristics of the Aegean Sea and the wider Mediterranean.
Bulgaria is newcomer to Argo, with two Bulgarian institutions take part in Euro-Argo: Physical Oceanography Group in the University of Sofia (USOF)
and Institute of Oceanology in the Bulgarian Academy of Science (IOBAS).
Bulgarian interests are mainly in monitoring the Black Sea and hope to use Argo data for assimilation into a Black Sea circulation model.
The Norwegian Argo programme is carried out by the Institute of Marine Research (IMR) as part of their environmental monitoring activities.
Float deployment started in 2002 and is often done in collaboration with the German Argo.
The Norwegian Argo programme focuses on the Nordic Seas for climate monitoring and research.
Ecosystem monitoring and research are also priorities, so some of the floats are also equipped with sensors for chlorophyll fluorescence and oxygen.
Institute of Oceanology Polish Academy of Sciences (IOPAS) is the polish ARGO project leader, and collaborate with the University of Gdansk.
IOPAS is particularly interested in the Nordic Seas, and use Argo data to investigate the Nordic Seas, especially Atlantic Water pathways and northward transports.