Building the UK BioGeoChemical Argo array: the UK contribution to a global integrated biogeochemical autonomous ocean sensing network

The ocean plays a vital role in sustaining life on planet Earth, providing us with living resources and regulating climate. Ocean observations are required to understand how the ocean and climate has changed in the past and to characterise the status of the marine environment and its resources today. Furthermore, global ocean observations are essential for skilful forecasts needed for planning, resource management, policy development and restoring ocean health. The Argo array of profiling temperature and salinity floats has transformed our ability to understand and predict sea level change, ocean heat content and sea surface temperature and their impacts on weather, climate, ecosystems, people and infrastructure. The Argo array has a dual role in providing initial conditions for predictive systems and in driving new process understanding that has led to model improvement. However, major ocean biogeochemical challenges including understanding the ocean's role in anthropogenic carbon uptake, de-oxygenation of the global oceans, and ocean productivity and health are not addressed by the Core Argo array.

BioGeoChemical Argo (BGC Argo) builds on the success of the Argo array through the addition of biogeochemical sensors for pH, oxygen, nitrate, chlorophyll, suspended particles and downwelling irradiance. Data from BGC Argo will drive a transformative shift in the understanding of biogeochemical cycling in the ocean and its dynamics at large scales: processes which have a profound impact on a rapidly changing climate, ocean productivity and health. Transformation will come through the acquisition of data with unprecedented space and time resolution, which was impossible before the development of BGC floats. BGC floats already produce more oxygen profiles per year than all research ships combined.

The BGC Argo Science and Implementation Plan calls for a global array. Pilot arrays have demonstrated the capacity to build the global array, but to date only a handful of the deployed floats have measured all 6 BGC parameters. The UK, through the G7 Future of the Seas and Oceans Initiative, has committed to contributing to the BGC Argo array. Having recently secured funding for 9 UK BGC floats (~15% of expected UK array), NOC has begun to deliver on that commitment and to develop a national facility for quality-control and distribution of the profile data in a timely way.

We will procure and deploy a further 16 BGC Argo floats in the Atlantic (~25% of UK array), all equipped with the 6 parameters required by international Argo. Resources for deployment and lifetime costs of providing quality-controlled, open-access data for this step-change in capability are in place through Climate Linked Atlantic Sector Science (CLASS) National Capability cruises and the British Oceanographic Data Centre. CLASS will fund a float coordinator to manage the floats and influence the development of the global array through the international Argo governance system.