The challenge
We need to know more about the ocean’s role in and response to a changing climate
The oceans store and transport vast amounts of heat. Three metres of ocean has the same heat capacity as the entire atmosphere, so it plays a large role in climate changes seasonally and over longer time periods.
The ocean has absorbed over 90 per cent of the excess heat trapped by the anthropogenic greenhouse effect caused by our CO2 emissions, and more than a quarter of those CO2 emissions thereby slowing anthropogenic climate warming.
Improving our understanding of ocean processes that take up the excess heat and CO2 will enable us to forecast climate and ocean conditions more accurately, including the impacts of the warming and ocean acidification (caused by the CO2 uptake) on marine ecosystems.
Our response
Monitoring our oceans with robotic floats
Diagram showing the Argo robotic float cycle process. First the float is dropped into the ocean. The float then descends to 2000 metres and its sensors are turned on. When it ascends the data is transmitted via satellite to the research station. The cycle continues.
We're part of a major international effort to improve our understanding of the ocean through the use of a global array of robotic floats, known as Argo floats.
Australia launched the first ten Argo floats in the Indian Ocean in 1999. There are now thousands of Argo floats in operation world-wide, and ArgoAustralia now launches more than 50 per year!
Explaining the Argo robotic float cycle process.
Argo robotic floats are the only means to collect the subsurface observations needed to provide year-round, near real-time information on ocean conditions.
The floats drift at depths of between 1 and 2 km, before ascending to the surface every ten days, measuring temperature and salinity as they rise. The data are then transmitted to satellites, before the float dives and starts a new cycle.
Some of the floats also measure additional quantities that inform us about the ocean's role in the CO2 uptake and its impacts, including:
- pH (a measure of the acidity induced by the CO2 uptake)
- dissolved oxygen (reflecting the intensity of both air-sea gas exchange and biological activity)
- dissolved nitrate (essential to plant growth)
- chlorophyll (the green plant pigment), total suspended particles via optical backscatter
- incoming solar radiation (which stratifies the ocean trapping heat and gases near the surface and drives plant growth).
Argo robotic floats can be deployed from research or commercial ships, and also from aircraft.
They are the only means to collect the subsurface observations needed to provide year-round, near real-time information on ocean conditions. They are about the size of a person.
A global initiative
Argo is sponsored by the World Climate Research Programme's Climate Variability and Predictability project (CLIVAR) and by the Global Ocean Data Assimilation Experiment (GODAE).
It is a pilot project of theGlobal Ocean Observing System (GOOS) and the United Nations Ocean Decade - The Science we need for the Ocean we want.
CSIRO operates Argo Australia, as a component of Australia's Integrated Marine Observing System (IMOS). Argo floats are deployed, real-time processed, and delayed-mode processed at CSIRO.
Argo Australia is operated by CSIRO with cash and operational support from the Bureau of Meteorology, financial support from IMOS, CSIRO, the Australian Antarctic Program Partnership, and the Australian Government Environment Department.
More information on Australian float deployments is available via the IMOS Argo facility and its biogeochemical sub-facility including how to access data.