Profiling float network reaches its goal

	Canadian Argo float being deployed in the Bering Sea on 24 October 2007 (Photo: Hiroshi Matsunaga)

On 1 November 2007, the broad-scale global array of temperature/salinity profiling floats, known as Argo, reached its initial target of 3000 operational profiling floats. The programme started in 1998 and planned to sample the world oceans for water temperature and salinity profiles to a depth of 2000m and to estimate the ocean currents at that depth at a horizontal resolution of 3° x 3°.

Argo data have permitted a reduction in the uncertainty of ocean heat storage calculation, thereby improving estimates and forecast of sea-level rise caused by thermal expansion. Argo is now playing a key role in improving seasonal climate forecasts. Its data are routinely being used in coupled ocean-atmosphere models, together with satellite products and other data from in situ observing systems.

The completion of this implementation phase has allowed more countries to be involved. More than 30 countries and the European Union are now participating in Argo. An effective data system capable of delivering real-time and delayed-mode data has now been developed, as well as a widespread user community covering both research and operational applications. Overall reliability of the system has been improved and the float lifetime extended to four years.

Sustainability over the decadal time-scale remains an issue, since most of the national Argo programmes are still supported through research funding. Sustain-ability is justified for both research and operational applications. Argo data are increasingly being used for ocean and climate modelling.

Argo is now between its implementation phase and its sustained maintenance phase, which will last for at least the next decade. It will optimize the array’s design, address new challenges (e.g. extending float life-time beyond fours years) and enhance further the quality and usefulness of the data. The value of Argo will be fully demonstrated and exploited.

The Argo array is the centrepiece of the in situ ocean observing system promoted by the Joint Commission for Oceanography and Marine Meteorology, co-sponsored by the Intergovernmental Oceanographic Commission of UNESCO and WMO. Argo is a pilot project of the Global Ocean Observing System and the Global Climate Observing System.

On 1 November 2997, Argo reached its goal of 3000 active floats (courtesy JCOMMOPS)