Understanding the wind-driven currents

Understanding the wind-driven currents has been a major concern of oceanography since Ekman’s pioneering paper in 1905. In the frequency domain, winds and currents are linked by the so-called transfer function. In a new paper, Lilly and Elipot (2021), we systematically analyze a general transfer function form, and show that it contains as special cases the results of a half-dozen earlier studies. This figure shows the transfer function magnitude with an infinite (left) or 50 m (right) boundary layer depth; the maximum near the inertial frequency, ω=-f, is the inertial oscillation response. Roman numerals mark regimes where different asymptotic behaviors are found to emerge. This unifying study is a step towards a better ability to understand and predict the near-surface currents.