Ocean Basin to Watershed Modeling of the North Pacific Provides a New Basis for Modeling Climate Change Impacts on Salmon, Introducing the SCHISM-based Model: CPOEM
The Columbia River Inter-Tribal Fish Commission (CRITFC), in partnership with NOAA and academia, has developed a new model for the Pacific Basin that seamlessly represents processes across ocean basin to estuary and watershed spatial scales. Ocean circulation models used to evaluate climate change impacts on salmon in the open ocean and coastal/estuarine domains have previously had fundamental limitations due to different models required for different spatial scales. Recent improvements in the ability of a varying-resolution (unstructured grid) circulation model to represent the eddying regime of the open ocean make it possible to create a continuous representation across basin-scale open ocean processes (such as the North Pacific Gyre currents and eddies), coastal processes (including upwelling and coastally trapped waves) and estuary and watershed processes (including river plumes, salinity intrusion in estuaries, and storm-driven rain runoff). The new model for the Pacific Basin extends from the Bering Strait to 30 degrees South latitude and incorporates high resolution representations of areas of interest, including the Columbia River estuary. It uses the modeling code SCHISM to provide a three-dimensional, tidal, baroclinic representation of the ocean. After minimal calibration, the model demonstrates cross-scale skill in representing ocean and estuary features during a one-year (2018) simulation, including basin-scale currents, coastal upwelling, coastally trapped waves, salinity intrusion within the Columbia River estuary, and basin-wide elevations, both tidal (median complex error in semi-diurnal tide of 0.08 m) and non-tidal (median root-mean-square error of 0.06 m). The Pacific model is forced using atmospheric models, river discharge, harmonic tidal models, and global ocean models at the boundaries, and it can be forced using global climate model results for climate change scenarios. It therefore has the potential to explore cross-scale interactions under climate change scenarios, such as interactions between changes in major currents and changes in coastal river plume size and timing. Although not included in the existing stage of development of this model, it can be extended to incorporate nutrient-phytoplankton-zooplankton-detritus (NPZD) models and its results can be incorporated into salmon life cycle and ecosystem modeling. Because oceanographic conditions experienced by salmon during their immediate entry and first year at sea are critical to overall survival and growth of a given year class, improving the resolution and quality of oceanographic data will help explain more variation in current and projected estimates of salmon productivity.
Seaton, C., A. Baptista, M. Swirsky, D. Graves, A. Kurapov, G. Seroka, and Y.J. Zhang. 2022. Ocean basin to watershed modeling of the North Pacific provides a new basis for modeling climate change impacts on salmon, introducing the SCHISM-based model: CPOEM. International Year of the Salmon Synthesis Symposium, October 4-6, 2022. Vancouver, Canada.