Watching over the world's oceans
Covering 72% of the Earth and supplying half its oxygen, oceans are our planet's life support system. They play a crucial role in distributing heat, carbon, oxygen, nutrients, and, of course, water around the world, influencing our climate and our weather. The effects of global warming on sea levels, currents and water heat are still only partly understood, making predictions for future climate conditions difficult. But a worldwide programme using thousands of plastic floats is currently monitoring the oceans and - with crucial help from European researchers - is finding answers to what moves the seas.
The EURO-ARGO research infrastructure is the European component of the programme, contributing one quarter of the international effort. That means deploying about 250 floats every year and maintaining an array of 800 floats at any given time (the average float lifespan is about four years). EURO-ARGO currently has about 500 floats in service, mainly in the Atlantic and Indian oceans, and it will be at least 2014 before the full array is deployed.
The EURO-ARGO preparatory phase, backed by a €3 million grant from the European Commission, helped establish a European legal structure for the programme, known as EURO-ARGO ERIC. Starting from 2013, this will allow European countries to better organise, develop and consolidate the European component of the global network.
The floats ride the ocean currents and descend into the water column down to 2,000m. They rise to the surface after about 10 days using a hydraulic piston to alter its volume. By then, they will have collected information on temperature and salinity - two essential climate variables describing the oceans’ physical and thermodynamic state. Upon surfacing, they send the data out by satellite. Each float acquires 200 profiles over a five-year lifetime.
The information from the floats will help paint a clearer picture of how climate change works, says EURO-ARGO’s project coordinator Pierre-Yves Le Traon. “Ocean measurements are essential if we are to understand the Earth’s climate, make predictions of how it will change under natural variability and human influences, and address such practical problems as sea level rise and regional changes in rainfall and temperature,” he says. “The evolution and performance of our array is monitored in near real time. Temperature and salinity observations are checked in real time through automated procedures”, he adds.
The ARGO data is assimilated with those from satellites into ocean circulation and climate models, in support of research and operational applications. The ARGO array is also integrated into the Global Monitoring for Environment and Security (GMES) and the Global Earth Observation System of Systems (GEOSS).
The ARGO programme has already gathered valuable insights, particularly on how rising water temperatures affect sea levels, and how salinity changes reflect a growing intensity in the global hydrological cycle. It is now the dominant dataset for basin-to-global scale physical oceanography, and over 200 research papers per year are now being published using ARGO data.