HF Radar Observations of Wintertime Surface Currents Over Hecate Strait, British Columbia

Abstract

ABSTRACT An oceanographic high-frequency radar system was deployed by Fisheries and Ocean Canada along Hecate Strait, British Columbia to strengthen regional marine safety, including search-and-rescue operations. The Hecate Strait CODAR system provides hourly surface currents on a grid that spans central-northern Hecate Strait at a horizontal resolution of 5 km. These observations are used to characterize regional tidal currents and the subtidal wintertime surface circulation. The HF radar currents are also used to assess results from the Coastal Ice Ocean Prediction System for the West Coast of Canada (CIOPS-W), a component of the pan-Canadian operational ocean modelling system. Comparisons of rotary spectra and tidal current ellipses with historical current metre observations show that vector currents from the Hecate Strait CODAR system are reasonably accurate and can be used to describe the circulation and variability of ocean currents over the strait on tidal and subtidal time scales. Variability of the subtidal flow, in particular the along-strait surface-layer transport, is closely related to local wind forcing and sea level variability. A vector regression to buoy winds demonstrates that the ocean response is highly anisotropic, with the magnitude and veering of the surface current strongly dependent on the direction of the wind. Comparisons with the CIOPS-W model currents show reasonable agreement with the HF radar currents, particularly with respect to the along-strait transport.