"The Euro-Argo infrastructure will be a major component of the Argo global in situ ocean observatory. The Argo network is a global array of autonomous instruments measuring temperature and salinity over the upper 2000 m of the ocean. Argo is an indispensable component of the Global Ocean Observing System required to understand and monitor the role of the ocean in the Earth’s climate system. Argo must be considered in its ensemble: not only the instruments, but also the logistics necessary for their preparation and deployments, field operations, the associated data streams and data centres. Euro-Argo will develop and progressively consolidate the European component of the global network. Specific European interest also requires a somewhat increased sampling in regional seas. Overall, the Euro-Argo infrastructure should comprise 800 floats in operation at any given time. The maintenance of such an array would require Europe to deploy about 250 floats per year. The main objective of the Euro-Argo preparatory phase will be to undertake the preparatory work needed to ensure that by 2010 Europe will be able to deploy and operate an array of 800 floats and to provide a world-level service to the research (climate) and environment monitoring (e.g. GMES) communities. The proposal will consolidate and broaden the European participation in Argo and will develop further a leading role of Europe in global ocean observations and in ocean and climate research. The main expected outcome of the proposal is an agreement between member states and other funding agencies for long term (> 10 years) operation of Euro-Argo. To reach such an agreement, it will be necessary to work on several key technical (float technology, data management and delivery system) and organizational (logistics for deployment, coordination of national contributions) issues, to consolidate and broaden the user community and to demonstrate further the impact and utility of the infrastructure for Europe."