Hood canal bridge effect on hydrodynamics and nearfield zone of influence

Hood Canal is a deep and long estuarine sub-basin within the Salish Sea that exhibits characteristics of classic fjords. Presence of the Hood Canal Bridge (HCB), a floating barge-like block near the mouth of Hood Canal is under investigation for potential environmental impacts on water quality and pelagic ecosystem. In this study, the effect of HCB on Hood Canal stratification and transport were evaluated using the Salish Sea Model, a 3-D hydrodynamic model with Hood Canal Bridge embedded at a high local resolution. The effects of the bridge as an obstruction to tidal currents and circulation were examined near the structure with the objective of characterizing the nearfield zone of influence (ZOI). This was accomplished through a combination of field measurements, and model simulations. ZOI was defined as the 3-D space near the floating bridge where ambient water properties were noticeably affected relative to background or natural water approaching the bridge during ebb or flood conditions. Field measurements included tides, currents, salinity, and temperature profile time series data collected from locations near the bridge over a 4-week period. These included stations upstream, downstream, and directly below the structure. The model results were in good agreement with the observed data. The simulated results show significant reduction of velocities in the surface layers near the structure. The Effect of HCB on temperature and salinity was also noticeable and extended over a larger zone predominantly during peak ebb and flood periods. HCB blocks the advection of warmer temperature and brackish water from the inner part of Hood Canal to the Salish Sea, creating significant backwater effect and associated temperature and salinity gradients during ebb as well as flood. ZOI(s) relative to the ambient current, salinity, and temperature structure were computed and will be presented

Vignette 13: The Salish Sea Model

Given numerous concerns related to the health of the ecosystem and the possibility of anthropogenic impacts—from population growth to climate impacts, such as sea level rise—scientists, engineers, and planners seek an improved basic understanding of the biophysical behavior of the Salish Sea. The Salish Sea Model (SSM) development was motivated by this urgent need for a comprehensive predictive model that could diagnose water quality issues and concerns and serve as a planning tool in support of Puget Sound restoration efforts. The SSM was developed by the Pacific Northwest National Laboratory in collaboration with the Washington State Department of Ecology (Ecology) and with support from the United States Environmental Protection Agency (USEPA)

Ocean acidification driven changes in pH exposure of zooplankton: projections from the Salish Sea model

The Salish Sea Model explicitly evaluates the dynamics of carbonate chemistry parameters (pH, DIC, Alkalinity) at relatively small spatial and temporal scales. These model components served as a basis for estimating the pH exposure dynamics of simulated zooplankton. Zooplankton were modeled assuming a variety of movement behaviors including passive drift with the currents, daily vertical migrations and directed movement toward food or way from unfavorable conditions. These movement behaviors capture the range of possibilities for many of the species in Salish Sea. The pH conditions from the Salish Sea Model included simulations from multiple seasons in recent years and projections of carbonate chemistry expected in the future from ocean acidification. The zooplankton behavior, season, specific location in the Salish Sea ,and changes from ocean acidification all influence the pH exposure trajectories. The analysis provides insight in to which combinations of features lead to the highest and lowest rates of exposure to potentially hazardous pH conditions

Challenges with accurate tracking of oil spill trajectories within Puget Sound

Risk of oil spill within the Salish Sea has recently been highlighted by the construction of Canada’s Kinder Morgan Trans-Mountain Expansion Project, which is expected to increase oil tanker traffic through the Strait of Juan de Fuca by over 400 tankers per year. Complex circulation patterns in this high-energy fjord complicates the tracking of spills to aid both prevention and response. PNNL’s Salish Sea Model has been refined for over a decade and represents the leading hydrodynamic model for the region. In a recent project, the Salish Sea Model was paired with the National Oceanic and Atmospheric Administration’s General NOAA Operational Modeling Environment (GNOME) and the National Energy Technology Laboratory’s Blowout and Spill Occurrence Model (BLOSOM) to recreate the 2003 Point Wells oil spill near Seattle, Washington. This was the first time that GNOME and BLOSOM were directly compared, highlighting differences in methodology and practice. Yet this was also an opportunity to optimize the Salish Sea Model for surface oil spills, understanding the specific challenges associated with the Salish Sea region. The challenges have been overcome and the Pt. Wells spill trajectory has been successfully reproduced. This project showcased the importance of correct hydrodynamics in a high-energy, enclosed estuary. Building on this experience equips the Salish Sea Model to inform planning and response activities that can protect vulnerable animals and habitat in this pristine environment

Development of a Hydrodynamic Model of Puget Sound and Northwest Straits

The hydrodynamic model used in this study is the Finite Volume Coastal Ocean Model (FVCOM) developed by the University of Massachusetts at Dartmouth. The unstructured grid and finite volume framework, as well as the capability of wetting/drying simulation and baroclinic simulation, makes FVCOM a good fit to the modeling needs for nearshore restoration in Puget Sound. The model domain covers the entire Puget Sound, Strait of Juan de Fuca, San Juan Passages, and Georgia Strait at the United States-Canada Border. The model is driven by tide, freshwater discharge, and surface wind. Preliminary model validation was conducted for tides at various locations in the straits and Puget Sound using National Oceanic and Atmospheric Administration (NOAA) tide data. The hydrodynamic model was successfully linked to the NOAA oil spill model General NOAA Operational Modeling Environment model (GNOME) to predict particle trajectories at various locations in Puget Sound. Model results demonstrated that the Puget Sound GNOME model is a useful tool to obtain first-hand information for emergency response such as oil spill and fish migration pathways

Puget Sound Dissolved Oxygen Modeling Study: Development of an Intermediate-Scale Hydrodynamic Model

The Washington State Department of Ecology contracted with Pacific Northwest National Laboratory to develop an intermediate-scale hydrodynamic and water quality model to study dissolved oxygen and nutrient dynamics in Puget Sound and to help define potential Puget Sound-wide nutrient management strategies and decisions. Specifically, the project is expected to help determine 1) if current and potential future nitrogen loadings from point and non-point sources are significantly impairing water quality at a large scale and 2) what level of nutrient reductions are necessary to reduce or dominate human impacts to dissolved oxygen levels in the sensitive areas. In this study, an intermediate-scale hydrodynamic model of Puget Sound was developed to simulate the hydrodynamics of Puget Sound and the Northwest Straits for the year 2006. The model was constructed using the unstructured Finite Volume Coastal Ocean Model. The overall model grid resolution within Puget Sound in its present configuration is about 880 m. The model was driven by tides, river inflows, and meteorological forcing (wind and net heat flux) and simulated tidal circulations, temperature, and salinity distributions in Puget Sound. The model was validated against observed data of water surface elevation, velocity, temperature, and salinity at various stations within the study domain. Model validation indicated that the model simulates tidal elevations and currents in Puget Sound well and reproduces the general patterns of the temperature and salinity distributions

Response of Salish Sea circulation and water quality to climate change and sea level rise

There is much interest in the Pacific Northwest community and water quality management agencies to better understand and predict long term changes in the Salish Sea water quality given periodic occurrences of hypoxia and evidence of coastal acidification. However, the projected interaction of riverine and estuarine systems under potential future climate-change scenarios is not well characterized in the Salish Sea area. In this study, the Salish Sea Model of circulation and water quality developed using FVCOM-ICM model was applied to provide insights on how estuarine/nearshore environments may be impacted in the future. It serves as a proof-of-concept assessment of the methods to functionally link downscaled outputs of CESM models for the Pacific Northwest (meteorology and biogeochemistry) to a marine circulation and water-quality model. We present simulated 100-year changes under the RCP8.5 scenario, including projected future increases in air temperature (≈+3.5˚), Pacific Ocean temperature (≈ +2.4°C), and river flow temperatures (≈+3.2°C), in combination with a projected sea level rise of +1.5m and future ocean chemistry changes. Our results show that strong vertical circulation cells in Salish Sea provide mitigation through mixing and continue to serve as a physical buffer, keeping water temperature cooler than over the continental shelf. Despite the mitigation effects, under RCP 8.5 scenario Salish Sea is expected to undergo several significant changes, including: temperature increases (+1.8°C), hypoxia zone expansion, and potential algal species shift (dinoflagellates: +196%; diatom: -14%). Snohomish Estuary, as an intertidal site example, is projected to experience 3 ˚C annual mean surface temperature increase and substantial seawater intrusion

Introduction

Introduction to the assessing, planning and adapting to climate change Impacts in Skagit River watershed session of the Salish Sea Conference

Eyes Over Puget Sound: Producing Validated Satellite Products to Support Rapid Water Quality Assessments in Puget Sound

Eyes Over Puget Sound (EOPS) is a rapid communication and outreach product developed by the Washington State Department of Ecology that provides a concise synthesis of near real-time data sources in Puget Sound, WA. Monthly EOPS reports summarize aerial photographic surveys, in-situ ferry observations, satellite products, CTD profiles, and mooring data within 2-days of completing each aerial survey. To facilitate the rapid development and synthesis of satellite information products, EOPS developed a framework for producing regionally-tuned products; validated using coincident ferry-based measurements of chlorophyll fluorescence, turbidity, CDOM fluorescence, temperature, and salinity. Daily ferry transects provide a consistent suite of high-resolution measurements necessary to characterize small-scale spatio-temporal variability across the large optical gradients that are present. Ferry data are made available within 24 hours and allow validation efforts to be performed on a daily-, sensor-, and image-specific basis. This framework has been used to validate and merge satellite products from a variety of platforms including MERIS, MODIS, HICO, and Landsat. Future efforts will utilize EOPS-validated satellite products to refine coupled 3-D hydrodynamic/water quality models currently being developed for the region

Salish Sea model: ocean acidification module and the response to regional anthropogenic nutrient sources

Several monitoring programs indicate the presence of lower pH and related changes in carbonate system variables in the Salish Sea. This project expands the existing Salish Sea Model to evaluate carbonate system variables. This project quantifies the influences of regional nutrient sources on acidification. The model accounts for Pacific Ocean upwelled water, regional human nutrient contributions, and air emissions around the Salish Sea. This effort also identifies geographical areas and seasons experiencing greater influence from regional sources of nutrients to Salish Sea waters. Results from this effort indicate that increased dissolved inorganic nitrogen, phytoplankton biomass, and non-algal organic carbon caused by regional anthropogenic nutrient sources can constitute significant contributors to acidification in the Salish Sea