Bridging scales and knowledge to improve present and future assessments of ocean health

Assessing the state of ocean health is crucial to gauge the magnitude of challenges and to evaluate the effectiveness of potential solutions. This requires bridging two complementary dimensions. First, at the level of biological, physical and chemical processes, spanning from the microscopic scale of marine microbes to the vast expense of ocean gyres; second, at the level of people’s expertise, by incorporating diverse forms of local, transdisciplinary knowledge into a global, interconnected understanding of ocean systems. Bridging scales and knowledge is also essential for refining projections of ocean health toward the end of the century. However, ocean exploration - which includes both observation and modelling across disciplines- faces limitations due to our restricted ability to observe the ocean synoptically, over long periods, and across all scales and relevant variables. In this presentation, I will first explain how and why different physical spatio-temporal scales must be reconciled and integrated to assess ocean health accurately. I will focus on primary production (PP) as key indicator, as it can be observed at multiple scales via satellites and integrates the dynamics of physics, chemistry and biology, while also supporting overall marine productivity. I will emphasize the key role of the ocean’s physical mesoscale to sub-mesoscale spectrum, which contains the majority of oceanic energy and remains largely unresolved in both local in-situ sampling and in Earth System Models. I will demonstrate how the inadequate representation of these energetic fine scales introduces significant uncertainty, leading to divergent projections of PP. Finally, I will showcase how bridging physical scales and knowledge systems, along with local and global perspective, can improve fishery management practices