Abstract
The development of the OASIS coupler started in 1991 in CERFACS. At that time, it was used by two climate modelling groups in France to couple two different atmosphere models to one ocean model. 30 years later, i.e. in 2021, the latest version of the coupler, OASIS3-MCT_5.0, was released. OASIS3-MCT is used today by about 60 modelling groups over the 5 continents to assemble more than 80 different coupled applications including ocean and atmosphere components but also sea ice, sea level, wave, ocean biogeochemistry, land, river routing and atmospheric chemistry models. The success of OASIS3-MCT is due to its key features in terms of performance, flexibility and low intrusiveness. And the developers’ constant care to provide detailed documentation, active user support and training also favoured its use by a large community. Its wide adoption is certainly also linked to its community governance. Since 2017 a formal Advisory Board, composed of 6 persons chosen among the main user groups, periodically reviews a development plan proposed by the developers based on the users’ feedbacks. In this presentation, we will first describe the different technical solutions and coupling frameworks that exist for code coupling in climate modelling and then briefly review the historical evolution of OASIS3-MCT. We will also present in more detail the recent developments and the plan of evolution foreseen in the framework of the COMPACT project funded by the French Agence Nationale de la Recherche under the TRACCS umbrella.

Sophie Valcke holds a "highly qualified" research engineer position at CERFACS where she is working on high-resolution atmosphere-ocean-ice coupled modelling. She is leading the team of 4 to 5 engineers developing the OASIS3-MCT coupler, used for climate modelling by about 65 groups around the world. Thanks to her expertise in HPC and code coupling for climate, Dr Valcke participates in different international committees, e.g. the Research and Innovation Advisory Group (RIAG) of EuroHPC JU, the Advisory Board of the ESiWACE3 Centre of Excellence, the organizing committees of the workshops on Coupling Technologies for Earth System Models and the ENES workshops on High-performance computing for Climate and Weather Committee. Dr Valcke was CERFACS Principal Investigator for the EU infrastructure project IS-ENES3 and the ESiWACE2 Centre of Excellence. These projects favour Dr Valcke's interaction with many climate modelling groups in Europe and with other groups internationally developing coupling frameworks.