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Subsurface currents in the Strait of Georgia, west of Sturgeon Bank Chang, Phillip Yit Kuen

Abstract

Spectral characteristics of sub-surface current and temperature records spanning 310-533 days from me Strait of Georgia near Sturgeon Bank are examined. Of particular interest are low-frequency fluctuations having, a characteristic period of 30 days. Typically, the energy of the low-frequency and tidal currents are equal at 50m (each about 40% of the total), and 10% and 10%, respectively, at 200m. Low-frequency currents are observed to be baroclinic and posses a lateral length scale less than 10km. Their generation mechanisms are not identified. The low-frequency fluctuations in sea-level and current have poor-to-fair coherence, while those in air-pressure and current have poor coherence. Low-frequency fluctuations in wind and current have fair coherence at the eastern mooring, and poor coherence at the remaining two moorings. Fluctuations in water temperature have a characteristic period of 300 days. Water temperatures at different locations generally have poor coherence except at the lowest frequencies where they are fair-to-good. Water temperature and current at the same location have poor coherence. Tidal currents are found to be ellipses, with the largest constituents being M² and K¹. The magnitude, shape .and orientation of the tidal current ellipses are time-dependent. Internal tides are suggested as an explanation.

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