Research

For at least 3500 years, the Indigenous people of the Pacific Northwest and Southeast Alaska have improved shellfish access and productivity through the use of clam gardens, low rock walls across embayments that extend the intertidal zone and create favorable conditions for clam growth. In the Pacific Northwest, clam gardens have become an important component of Indigenous resurgence as communities restore existing gardens and build new ones. This project, funded by the Puget Sound Partnership and in collaboration with WWU's Coastal Communities and Ecology Lab (Marco Hatch), has the following three objectives:

1. Determine which physical processes (e.g. tides, winds, waves, and diurnal heating) are most. important in determining residence time and water properties in clam gardens.

2. Assess how tidal variability and variability in physical forcing change the relative importance of these processes in determining residence time.

3. Quantify the garden wall’s impact on wave dynamics by determining the amount of wave energy dissipated at, reflected by, and transmitted past the wall.

To achieve these goals, EHL is assisting with long term water property monitoring in a local clam garden, and conducted a two week observational field campaign in June 2024 to assess clam garden circulation. 

Collaborators: Marco Hatch (WWU ESCI), Erika McPhee-Shaw (WWU ESCI).

Westward-propagating Caribbean Current eddies modify the circulational structure in the western Caribbean Sea, influencing the circulation of the Panamá–Colombia Gyre (PCG) and coastal currents hundreds of kilometers to the south of the eddies’ mean trajectory. This project used 22 years of output from the Hybrid Coordinate Ocean Model and a potential vorticity balance to show that coastal currents in the PCG region vary by a factor of 2 in phase with the passage of a Caribbean Current eddy over the 116-day average eddy period. An annual ensemble average PV balance in the gyre region shows that the eddy influence in this region is higher between August and October. Correspondingly, the range of coastal currents in the gyre region over an eddy event is modestly influenced by the strength of eddy forcing. Eddy influenced reversals in the coastal current can occur between November and July at Bocas del Toro and year-round at Colón. Such coastal current reversals are important for the alongshore transport of larvae, freshwater, and chemical tracers.

Collaborators: Kristen Davis (Stanford), Geno Pawlak (UCSD/Scripps), Sarah Giddings (UCSD/Scripps), Annie Adelson (Scripps), Rachel Collin (STRI)

Bahia Almírante is a frequently hypoxic multiple inlet estuary on the Caribbean coast of Panama that is thought to be ventilated by advection of denser offshore water through its channels and into the oft-hypoxic back bay in a process similar to deep water renewal in fjords. In this project, we developed an instance of the Regional Ocean Modeling System (ROMS) to realistically represent the bay, in order to assess questions such as the following:

• What is the role of coastal currents in generating mean flow through the inlets of Bahia Almírante?

• How is hypoxia in the bay influenced by freshwater forcing in the system, such as rainfall and the nearby Changuinola river plume?

• How are these local processes linked to mesoscale and large-scale processes such as the Caribbean Current eddy field?

Collaborators: Kristen Davis (Stanford), Geno Pawlak (UCSD/Scripps), Sarah Giddings (UCSD/Scripps), Annie Adelson (Scripps), Rachel Collin (STRI)

Hood Canal, located in Washington State, is a long inland extension of the Salish Sea. The Canal is narrow, with sills that limit exchange with the rest of the Salish Sea, leading to hypoxic conditions which threaten the critical local shellfish industry. In this project, EHL members used output from the LiveOcean numerical model, run by the University of Washington, nutrient sampling from July 2022, and long term nutrient data from the Washington State Department of Ecology (DOE) to better understand the physical processes that may contribute to hypoxia in Hood Canal. Hood Canal is a nitrogen-limited system, so large fluxes of dissolved inorganic nitrogen (DIN) can lead to algal blooms and eutrophication, contributing to the development of hypoxic conditions. EHL members worked to assess the seasonality of the Hood Canal DIN budget, how advective and diffusive processes balance denitrification, and how these physical mechanisms relate to the development of hypoxia in the system. Future work to come!

Collaborators: Dr. David Shull (WWU-ESCI)