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Date of Award

Summer 2025

Document Type

Masters Thesis

Department or Program Affiliation

WWU Graduate School

Degree Name

Master of Science (MS)

Department

Environmental Sciences

First Advisor

McPhee-Shaw, Erika E.

Second Advisor

Mickett, John B.

Third Advisor

Kastner, Sam

Abstract

The Salish Sea is a complex estuarine system with cultural, economic, and biological significance for multiple nations. The circulation of the Salish Sea is dependent on tides and density-gradients driven by freshwater introduced into the system primarily from rivers. The discharge of these rivers is being impacted by climate change; with less snowpack and more rain in the winter months the average summer river discharge is weakening in response. In addition, record-breaking atmospheric heatwaves accelerate glacial recession and anomalous flooding events in the summer. This research explores the impact that these atmospheric heatwaves may be having on the circulation of the Salish Sea, with a focus on the exchange between Hood Canal and Admiralty Inlet. I hypothesize that anomalously high river discharge out of the Skagit River impacts the along-channel density gradient between Admiralty Inlet and Hood Canal that weakens the deep-water inflow over the sill into Hood Canal. Using publicly-available monitoring data, I explored the available time-series spanning 2006-2023. Within this historical record 2006, 2008, and 2021 show that anomalously high river discharges out of the Skagit River weaken deep-water inflow over the sill between Admiralty Inlet and Hood Canal. Additional investigation shows that this mechanism is modulated by the tides, requiring the freshwater discharge to align with a strong tidal signal that vertically mixes the water to depths below 80 meters. The year 2020 shows when river discharge corresponds with a neap tide there is not any noticeable change to the deep-water exchange.

Type

Text

Keywords

Hood Canal, Salish Sea, Admiralty Inlet, Heatwaves, Physical Oceanography, Circulation, Skagit River, River Discharge, Climate Change, Density Gradients

Publisher

Western Washington University

OCLC Number

1534458958

Subject – LCSH

Heat waves (Meteorology)--Salish Sea (B.C. and Wash.); Physical oceanography--Salish Sea (B.C. and Wash.); Ocean circulation--Salish Sea (B.C. and Wash.); Climatic changes--Salish Sea (B.C. and Wash.)

Geographic Coverage

Salish Sea (B.C. and Wash.)

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

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