A Wind-Forced Ekman Spiral as a Good Statistical Fit to Low-Frequency Currents in a Coastal Strait

Abstract

Ekman's classical analysis of wind-driven currents is a fundamental component of the modern circulation theory of the oceans, but there have been few good observations of the predicted Ekman spiral, where the velocity vector rotates clockwise in direction (in the Northern Hemisphere) and decays exponentially in magnitude with increasing depth. An analysis of recent cyclesonde velocity measurements based on the use of empirical orthogonal functions, however, suggests that a classical Ekman spiral was a good statistical fit to a significant portion of the low-frequency current fluctuations in the Strait of Georgia, British Columbia, for fluctuation periods of about 5 to 10 days.