The NAOS (Novel Argo Observing System) project, co-supervised by Ifremer and Sorbonne University, was the winner of the first wave of the EQUIPEX (Equipments of Excellence) call for projects launched as part of the French government's "Grand Emprunt" programme, and held its final meeting on 17 September. The project received €8 million in funding from the French National Research Agency and ran from 2011 to 2020: 10 years of development that have given France and Europe a new generation of autonomous Argo robots capable of meeting the future challenges of ocean observation.
The international Argo programme and its European and French contributions
Thanks to its 4,000 profiling floats (small autonomous robots) that measure temperature and salinity from the surface to 2,000 metres below the surface of the oceans, the international Argo programme, which brings together nearly 30 countries, has revolutionised global ocean observation. It is the world's first real-time in situ ocean observation network, an essential complement to satellite measurements for observing, understanding and predicting climate change, and characterising the impact of climate change on the physico-chemical properties of the ocean and on marine ecosystems.
A legal structure (Euro-Argo ERIC) was set up in 2014 to organise the European contribution to the network. It is coordinated by France and brings together 12 European countries. The French contribution to the Euro-Argo ERIC (Argo France) is a Very Large Research Infrastructure (TGIR) of the Ministry of Higher Education, Research and Innovation (MESRI). Argo France includes the coordination, procurement and deployment of floats, data processing and interfacing with the user community. France contributes around 10 % to the global network and hosts one of the two global processing centres (the Coriolis data centre operated by Ifremer).
Maintaining the Argo network over the coming decades is a major scientific challenge. In his opening speech at the 15th Assises de l'Economie de la Mer, the French President himself stressed the importance of Argo for ocean and climate research.
The NAOS Equipex project: strengthening France's contribution to the European network
Improving our knowledge of the ocean's role in climate also requires new observation tools. To meet these needs, NAOS has developed and validated the new generation of Argo profiling floats: floats that are more durable and 'intelligent', able to carry more sensors (particularly for marine biogeochemistry) and reach the most remote areas of the ocean, such as the deep ocean (4,000 m) and the polar regions.
Drawing on the technical and scientific experience of the NAOS consortium, three pilot experiments have been carried out:
Monitoring and better understanding the biogeochemical state of the Mediterranean Sea. A fragile basin subject to unprecedented anthropogenic pressure, the Mediterranean was the ideal 'playground' for demonstrating the effectiveness of NAOS profiling floats equipped with biogeochemical sensors as scientific instruments of excellence.
Exploring the dynamics of phytoplankton under the Arctic ice. One of the planet's most hostile natural environments, the Arctic plays a critical role in the climate machine. Under the ice, life has adapted and phytoplankton have found an ecological niche that is very difficult to observe. Floats, developed under NAOS funding, capable of 'wintering' under the ice to resurface when the ice melts, have been deployed there, in close partnership with Canadian teams specialising in the region.
Observing the deep dynamics of the Atlantic Ocean. In the North Atlantic, the deep plunge of surface waters is the main 'engine' of global ocean circulation and the storage of excess heat and CO2 due to human activities, thus contributing to the ocean's role in regulating the climate. NAOS floats capable of reaching these deep layers were deployed to study ocean circulation, which is still largely unknown, and its role in redistributing climate signals. The floats were also equipped with oxygen sensors to monitor and understand the ocean's capacity to oxygenate its deepest layers.
Major technological and scientific advances
Strengthening France's contribution to the international Argo network. Deployment of 100 floats over the period 2011-2019. France's contribution to the network is now 10% and represents more than 30 % of the European effort.
Significantly improved performance (lifespan, reliability) for the new generation of French Argo floats.
A new float capable of tracking climate change at depths of 4,000 metres.
Floats with improved biogeochemical sensors.
Intelligent floats capable of exploring polar zones and detecting the presence of ice.
First demonstration of an operational network of Argo floats with biogeochemical sensors at the scale of an ocean basin: implementation and maintenance of the network, real-time processing and quality control, integration with models.
First demonstration of the contribution of Argo floats with biogeochemical sensors for monitoring the Arctic Ocean and changes in its primary production
Remarkable scientific advances in the understanding of biogeochemical cycles in the Mediterranean, the Arctic and the deep ocean of the North Atlantic. More than 40 scientific publications based on the unique datasets collected during the three NAOS pilot experiments.
A strong partnership between the public and private sectors
The NAOS project is organised around a strong partnership between Ifremer (project leader), Sorbonne University (project co-leader), CNRS, UBO/IUEM, Shom and private companies: CLS for the satellite telecommunications aspects and the SME nke instrumentation responsible for the industrialisation, production and marketing of the Argo floats manufactured in France.
NAOS has had a catalytic effect in consolidating and strengthening nke's global competitiveness. Nke now ranks 2nd among industrial manufacturers of Argo profilers in terms of the number of active floats. This very good progress corresponds to an increase in nke's market share by a factor of 2 compared with the pre-NAOS period. The integration and performance analysis of Argos-3 technology carried out within NAOS has been essential for CLS to prepare its future satellite telemetry services (Argos-4, Kineis).
The future of NAOS: addressing the issues of the ocean's role in climate change
Building on the technological and scientific advances made by NAOS, France is proposing to implement its contribution to the new operational phase of the international Argo programme over the period 2020-2030, with an extension to the deep ocean (Deep Argo) and biogeochemistry (BGC-Argo).
This new phase of Argo is associated with major scientific challenges in the study of ocean evolution and climate change, in particular questions about the role of the deep ocean in the planet's energy balance, the oceanic pumping of CO2, ocean acidification, deoxygenation and the evolution of ecosystems and living resources. It is also essential for the monitoring and operational forecasting of the oceans implemented by the European Copernicus programme and its marine service piloted by France (Mercator Ocean International).