Wind Waves in the Strait of Georgia

Abstract

ABSTRACT The Strait of Georgia, British Columbia, Canada, is an important ocean region in which wave and weather conditions can vary rapidly in time and space because of the complex mountain topography that surrounds it. Here we analyze existing observational data and a newly developed near real-time numerical wave model, forced by modelled local winds and ocean currents, to characterize the surface wave conditions of the Strait under a variety of wind and weather conditions. Wave heights are generally largest in the northern Strait. However, we find that there are some deficiencies in the existing observational data, with buoy measurements in the northern Strait overestimating wave heights by as much as 0.4 m. The wave modelling also shows that strong tidal flows near Discovery Passage and Boundary Pass lead to increased wave heights, but current-related increases are not predicted near Sand Heads because of deficiencies in the numerical ocean current model. Outflow wind conditions in the Fraser Valley result in large waves south of Point Roberts but Howe Sound outflows do not noticeably affect significant wave heights offshore of Howe Sound. Stokes drift associated with surface waves can cause surface drifts as large as 20% of the directly wind-driven surface currents but is minimal for winds less than about , which characterize the Strait most of the time. Whitecap fractions throughout the Strait are similar to open-ocean conditions (i.e., 1–2% at moderate wind speeds) but about twice as high in the southern region of the Strait during strong outflow conditions.