Gathering users and developers to shape together the next-generation ocean reanalyses

Ocean reanalyses are reconstructions of the past ocean state combining ocean numerical models and Earth observations through data assimilation techniques. As a result of their temporal and spatial consistency and continuity compared to Earth observations only and their high accuracy and quality compared to pure numerical model simulations, ocean reanalysis data are widely used in the scientific community (e.g., ocean and climate process studies) and private sectors (e.g., operational planning, shipping, and fisheries). For almost a decade, the Copernicus Marine Service has provided users with high-quality, regularly extended global and regional ocean reanalyses. The objective of this workshop was to gather the international community to 1) understand the users’ needs for ocean reanalyses, 2) identify the strengths and weaknesses of current ocean reanalyses, 3) establish the way forward toward the next generation of ocean reanalyses by improving different aspects of these products to meet users’ needs and science ambitions, and 4) improve collaborations within the community. The 3-day workshop was held in Toulouse (France) and brought together ocean reanalysis users, producers from European Copernicus services and beyond, and scientific experts on different aspects (data assimilation, ocean models, and observations). The workshop’s hybrid format (online and in person) enabled us to welcome around 60 people in person and 1400 registrations online, with 700 unique connections on day 1, 350 on day 2, and 250 on day 3. The key findings of each objective are given in the following sections; the last section highlights the next steps the ocean reanalyses community will carry out.