Marine environmental prediction through improved biogeochemical models

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Anthropogenic perturbations of the global carbon and nitrogen cycles are altering fundamental physical and chemical properties of the ocean including water temperature, vertical stratification, circulation, pH, nutrient regimes and oxygen levels. It is expected that these changes in environmental conditions will strongly affect planktonic communities (which support the marine food web and play a major role in regulating the ocean’s uptake of carbon) and higher trophic level species like fish, bivalves and crustaceans (which are of commercial importance). Numerical models that accurately simulate physical, chemical and biological processes are a key tool for describing current and future environmental ocean conditions; however, a paucity of detailed ocean observations has severely limited efforts to critically evaluate models and improve their realism. To date there is no consensus on an appropriate biogeochemical model structure, and model projections of how ocean conditions will change in the coming century vary dramatically. Furthermore, model projections of future conditions (including those of the IPCC) rely on global models that lack the spatial resolution to adequately represent coastal regions (defined here to include continental shelves, i.e. regions with water depths <200m). Yet coastal processes have been shown to significantly affect global element cycles, and the coastal ocean is experiencing some of the fastest changes and is of most direct importance for human activities. The long-term objective of my research program is to develop models that better predict how natural variability, human pressures and climate change affect marine ecosystems now and in the future. The projects proposed here aim specifically at improving biogeochemical models in two key aspects: by combining models with new data streams from a range of ocean observing systems in order to improve process-level representations and parameterizations (Theme 1), and by improving the representation of biogeochemical processes in shelf regions through highly resolved regional models with dynamic benthic-pelagic coupling (Theme 2). Theme 1 takes advantage of recent progress in the development of autonomous oceanographic platforms and compact, low-cost sensors for measuring many important biological and chemical quantities in the ocean. The developments allow us to gather observations at ecologically relevant spatial and temporal scales and offer enormous potential for improving biogeochemical models. Theme 2 directly addresses a major shortcoming of current models, namely the lack biogeochemical interaction between sediments and water column. Prior research has shown that the exchange of constituents between sediments and the overlying water column is of major importance in determining productivity and environmental conditions in coastal systems unlike in the deep ocean where such exchange is weak. At present models either neglect or crudely parameterize this interaction. Biogeochemical models are and will continue to be essential tools in assessing, understanding and projecting the environmental changes affecting coastal and open ocean ecosystems. Further development of these tools is of global relevance and of strategic importance for Canada given its long coastline, its dependence on coastal resources and its commitment to implementing an ecosystem approach to ocean resource management. The program proposed here will lead to concrete model improvements.