Thermal gradients in Fisherman’s Bay

Fisherman bay, located on  Lopez Island WA, has a well marked presence of human activities, including the presence of a bordering residential community, several marinas and intense boat traffic. The bay is relatively shallow, with an average depth of FB.pngapproximately 4 meters and horizontal dimensions of 2 km by 0.5 km. It has a narrow, elongated and irregularly curved entrance on the north that is nearly 50 meters wide and 500 meters long, which connects the bay to a deep channel (100 m) located between the Lopez Island and San Juan Island. In the south of the bay there is a connection to an extremely shallow pool (1 m), with an area equivalent to 15% of the bay’s area. This area dries during strong ebb tides, and is thought to possibly serve as a source of heat to the southern region of the bay.

Temperature is the main control on density and stratification in Fisherman Bay. Temperatures in the bay range from about 10 to 15°C, with spatial and temporal distribution controlled mainly by tidal advection and incoming solar radiation. The propagation of a tidal intrusion front is a main mechanism of heat exchange between the bay and channel outside the mouth.  The shallow shoals, especially in the southernmost region of the bay serve an important role in regulating heat transport into the deeper channel of the bay during ebb tide.

This project was a part of the Estuarine and Coastal Fluid Dynamics course at the University of Washington Friday Harbor Laboratory in summer 2012.