2.1 Ferry-Based Velocity Measurements through Admiralty Inlet, Puget Sound, Washington

Monday, 23 January 2017: 4:00 PM
Conference Center: Chelan 4 (Washington State Convention Center )
Maricarmen Guerra Paris, University of Washington, Seattle, WA; and J. Thomson, C. Maloy, C. Krembs, and B. Sackmann

Admiralty Inlet is the gateway between Puget Sound and the Strait of San Juan de Fuca (and thus the Pacific Ocean). Tidal and estuarine circulation here is complex, with currents exceeding 3 m/s and large variations in fresh water input to the system. Understanding this circulation and subsequent effects on water quality requires detail space and time observations of the currents across Admiralty Inlet. The Washington State Department of Transportation (WSDOT) Ferries, which run year round through Admiralty Inlet, provide an excellent cost-effective platform to mount instruments and obtain long time series of currents.

In cooperation with the WSDOT, two down-looking Acoustic Doppler Current Profilers (ADCPs) were installed onboard the MV Kennewick and MV Salish ferries. The two ferries, which run the Coupeville - Port Townsend route, provide full depth profiles of currents across Admiralty Inlet continuously since May 2014. These measurements are part of the Washington Department of Ecology’s participation in the National Estuary Program funded by the Environmental Protection Agency.

Measurements are ongoing and raw data are available at the project’s web site[1]. The data set includes vertical velocity profiles, bottom tracking depth and velocity, and navigation information. Quality-controlled binned data are available at the NVS Data Explorer platform[2] showing hourly prevailing currents magnitude and direction.

Data from the ferry ADCPs are tested to distinguish tidal currents. Harmonic analysis of binned time series of horizontal currents is performed using UTIDE. Results provide M2 tidal current amplitudes across Admiralty Inlet. The results show a large spatial variability of the M2 tidal current component. Lower amplitudes are observed in the shallow area to the south of Port Townsend, while stronger amplitudes are observed at mid channel, where a deeper narrow channel exists. Obtained M2 amplitudes agree well with previously reported values from stationary measurements.

- Indicates paper has been withdrawn from meeting
- Indicates an Award Winner