By Amber Brooks

What’s with the name? Name reflects Greek Mythology relationship between the vast network of floats and the Jason satellite altimeter mission Years before the Trojan War, Jason set forth on a ship to find the Golden Fleece that would give him air to the throne in Thessaly. The ship was named Argo after its builder Argus, and the crew was known as the Argonauts.

About Argo drifting CTD float Collect data down to a depth of 2,000 meters allows the globe to continuously monitor temperature, salinity and velocity of the upper ocean on a system instantly displays data within hours of collection for public and scientific use network of 3,388, as of May 21, 2009

Float Distribution as of May

CAL Sea 2008 Vallejo, CA – Honolulu, Hawaii 8 floats deployed

Argo Objectives quantify and describe the upper ocean and climate variability from a smaller scale of months to several years at a time enhance the Jason altimeter by way of measuring temperature, salinity and velocity with accuracy great enough to calculate sea surface height with great accuracy provide a base for climate modeling of the ocean- atmosphere and documentation of the decadal variability in climate

Float Mechanics & Subsystems 3 different float designs Pacific Marine Environmental Laboratory (PMEL), uses: 1) a 10 day interval where fluid is pumped into an external bladder causing a change in density, resulting in a gradual rise to the surface 2) bladder hydraulics as well as microprocessors that deal with function control/timing, and a transmission system that controls data communication with satellites. 3) weighs approximately 25kg (55lbs), has a maximum operating depth of 2000m (6,561ft) and a crush depth of 2600m (8,530ft)

Float method for data collection Floats spend most of their lives at “parking depth” or the depth at which they are stabilized by obtaining neutral buoyancy. Neutral Buoyancy: float’s density is equal to the ambient pressure and a compressibility that is less than sea water After several days at “parking depth” the float rises to the surface taking 200 pressure, temperature, and salinity measurements, remaining at the surface for 6-12 hours talking to satellites. Once the transmission is complete, the bladder deflates, returning the float to its original density and it sinks to parking depth for another cycle.

Above: temp/salinity profile after drifting period Right: Drifting track prior to profiling Cal Sea Float #4

Argo data = Superior data - lack of seasonal bias -efficient automatic data management within a 24 hour period - international collaboration

Float of the Month January 09 -deployed at the Greenwich Meridian into the southern limb of the Weddell Gyre in December remarkably long operating time in seasonally ice covered areas is due to a special Ice Sensing Algorithm (ISA) -ISA - prevents the float from surfacing in ice covered waters and hence, protects the float from being destroyed or damaged by the ice. - The float aborts the ascent if the median of the temperature between 20 and 50 m depth is less than -1.79°C, which is almost the freezing point of sea water at the sea surface. AWI-Argo float with WMO ID

Float of the Month May 2008 APEX float - WMO# takes island vacation -drifted into the Malum Atoll of Papua New Guinea -Scientists feared it would no longer operate -Swept east to west during data communication with satelittes

Data Access Argo Information center in Toulouse, France manages float information National data centers then receive the data and erroneous data is flagged and all data is passed on to: Argo’s two Global Data Assembly centers (GDACS) in Brest, France and Monterey, California. data is made publically accessible through GDACS by the Global Telecommunication System (GTS), and are updated instantaneously - free & easy access to data by float WMO#

Data Distribution

International Effort 23 international participants (countries) Contributions range from a single float to the United States contribution of roughly 50% of the global network. Mechanisms for funding vary between countries and include over 50 research and operational agencies. Argo deployments began in 2000 and by November 2007 the array is 100% complete.

Importance of Argo As more and more becomes known about ocean variability the need for Argo observations will increase. Technological advance and the global distribution of the array of floats will evolve as instruments and models are improved. With present severe climate changes and the massive climate role of the ocean, now and into the future, we as a global community will need Argo.

QUESTIONS?