The Salish Sea is a rapidly growing region that supports significant maritime commerce, and ship traffic which is expected to increase continuously in the coming years. In addition, the Salish Sea receives wastewater discharges from 99 wastewater outfalls from major cities, including Seattle, Tacoma, Everett, and Bellingham, in US and Victoria and Vancouver in Canada. In recent years millions of gallons of untreated wastewater have been accidentally discharged directly into Puget Sound due to overload and equipment failure. These events along with increased risk associated with potential maritime accidents and spills have resulted in heightened community-wide interest in real-time oceanographic information. Current predictions with sufficient spatial resolution and accuracy are needed for use in risk management from exposure to potential spills and in support of navigation and maritime emergency response. The National Oceanic and Atmospheric Administration/ National Ocean Services (NOAA/NOS) identified the Salish Sea region of the Pacific Northwest as a major data gap and the development of an Operational Forecast System (OFS) for the Salish Sea has become a high priority. In addition to NOAA mission goals and priorities related to navigation, the annually recurring hypoxic events, exposure of shellfish farms to corrosive waters, seasonal harmful algal blooms, occurrences of shellfish poisoning, and exposure to wastewater and stormwater, are ecosystem management related challenges faced by the communities that need and would benefit from real-time information from an OFS for this Salish Sea region.
Figure 1 below shows the overall Salish Sea Model domain (inset) along with a close up of the inner Salish Sea region.
Figure 1. (a) The Salish Sea study area defined by major basins – Puget Sound, the Strait of Juan de Fuca, and the Strait of Georgia) along with the overall model domain (inset). SSMHR model grid coverage for selected basins in the Salish Sea (b) South Puget Sound, (c) San Juan Islands, (d) Puget Sound Central Basin, and (e) Strait of Juan De Fuca
Through the IOOS Coastal Ocean Modeling Test Bed Program (COMT), and in collaboration with IOOS regional association NANOOS, PNNL initiated a project titled “Towards an Operational Forecast System for the Salish Sea”. The objective was to transition the Salish Sea Model (SSM) developed by PNNL to an operational forecast system status, to be maintained by NOS, following major improvements in the form of grid resolution refinement and detailed skill assessment to reach the required readiness level. One obstacle to refinement and the development of a shoreline resolving intertidal scale model has been the lack of current measurements with sufficient coverage which could be used for robust model validation and testing. New acoustic doppler current profile (ADCP) data collected by the National Oceanic and Atmospheric Administration (NOAA) Center for Operational Oceanographic Products and Services (CO-OPS) from 135 stations in the Salish Sea over the years 2015 to 2017 fully addressed this data gap. The COMT project supported by this data set has led to the development of a high-resolution version of the coupled hydrodynamic and biogeochemical (in progress) SSMHR. (see Premathilake and Khangaonkar 2022 for initial model validation and skill assessment results).
Figure 2 below demonstrates the skill of SSMHR in resolving the spatial distribution of tidal currents within the Salish Sea domain affected by complex shorelines and multiple mid-channel islands.
Figure 2. The comparisons of tidal ellipses generated from depth averaged currents simulated by SSMHR. and the ADCP data collected by NOAA-NCOP from 2015 to 2017.
An example animation of currents and a hypothetical oil spill transport from the Haro Strait region near San Juan Islands is shown below. (Hypothetical Oil Spill Simulation in Haro Strait, WA)
NOS expressed interest in upgrading and consolidating the Columbia River domain into one of the existing larger domain OFSs. Given the complexity of the Columbia River estuary shoreline, NOS requested that the Columbia River domain be included in the Salish Sea Operational Forecast Syatem based on its similar unstructured grid finite volume formulation and funded the effort independently through the regional association NANOOS. The resulting model is the Salish Sea & Columbia River Operational Forecast System (SSCOFS), which has also achieved a readiness level for transition to NOS. The SSCOFS, in addition to the Salish Sea, incorporates 146 miles of Lower Columbia River domain from Astoria, OR at the mouth, to Bonneville Dam.
Figure 3 shows below the evolution of the original Columbia River grid from SSM, to the intermediate refined version, and the final version of the Columbia River region of SSCOFS model grid. In parallel with grid refinement, the existing bathymetry (originally from the Eastern North Pacific ADCIRC model grid) was also updated using a more detailed and updated bathymetry provided by NOAA from the CREOFS.
Figure 3: Columbia River estuary region grid of the Salish Sea Model (a) Original placeholder coarse scale grid in SSM, (b) Intermediate refinement as part of the SSM-OFS model version grid, and (c) Final version of refinement implemented in SSCOFS model.
Operational forecast results are under Beta Testing and expected to be available from NOS in CY24