Coastal Ocean Forecasting Science supported by GODAE OceanView Coastal Oceans and Shelf Seas Task Team (COSS-TT)—Part II

International audienceThe regional and coastal ocean, as a complex interface area where land, hydrology, atmosphere and ocean interact, concentrates a wide range of actors dealing with increasing socio-economic and environmental issues. Under the pressure of the impacts of climate change, forecasting the coastal ocean remains a key challenge. The international Coastal Ocean and Shelf Seas Task Team (COSS-TT) community within the OceanPredict program (former GODAE OceanView - https://www.godae-oceanview.org/) fosters multidisciplinary research efforts dedicated to the coastal ocean from the land/ocean interface to the shelf/open ocean exchange regions, in support of regional and coastal ocean forecasting. Following the first topical collection (De Mey et al. 2017), this second one offers research conducted within the COSS-TT themes. After a successful 6th international COSS-TT meeting in 2018, new steps were outlined in the integration of knowledge and capabilities in regional and coastal ocean forecasting. Two major community events defined these next steps for ocean prediction (GODAE OceanView Symposium 2019 - OceanPredict '19 - http://oceanpredict19.org/) and ocean observation (OceanObs’19 - http://www.oceanobs19.net/). The OceanObs’19 conference called for the global ocean observing community and users to “advance the frontiers of ocean observing capabilities from the coast to the deep ocean... at the boundaries between the ocean and air, seafloor, land, ice, freshwater, and human-populated areas” and to “improve the uptake of ocean data in models for understanding and forecasting of the Earth system”. These statements emphasize the need to improve the synergy between model and observations to develop regional and coastal ocean observing and forecasting capabilities (De Mey-Frémaux et al. 2019; Davidson et al. 2019). These 2018-2019 initiatives are well aligned to the scientific foundation of the United Nations Decade of Ocean Science for Sustainable Development (2021-2030). The COSS-TT community appears as a key actor of Ocean Decade Challenges related to regional and coastal ocean prediction (for example CoastPredict: Observing and Predicting the Global Coastal Ocean - https://www.coastpredict.org/).In this framework, the COSS-TT community centered this second topical collection around scientific priorities in agreement with ongoing open research fields and new identified priorities (in bold are addressed priorities in this second topical collection): (a) advances in integrated, multi-platform, long-term monitoring of physical, geochemical and biological parameters in coastal regions and coastal observatories; (b) development of fine-scale coastal ocean models; (c) downscaling approaches from large-scale to regional and coastal-scale models (methods for quantitative assessment, regional and coastal array design, downscaling approaches and data assimilation and predictability in coastal ocean forecasting systems); (d) coastal-scale atmosphere-wave-ocean couplings, (e) ecosystem response to physical drivers; (f) probabilistic approaches and risk assessment in the coastal ocean (including extreme events, impact and signature of climate change, science in support of the mitigation of coastal hazards); (g) science in support of applications in coastal oceans and (h) synergy between coastal modelling and coastal altimetry