Inertial Oscillation

An inertial oscillation is the free circular motion of a water parcel under the Coriolis force alone, after a wind impulse, with no pressure gradient. The parcel traces a clockwise circle in the Northern Hemisphere at the inertial period T = 2 pi / f, where f is the Coriolis parameter: about 17 hours at 45 degrees latitude and 24 hours at 30 degrees. Storm passage commonly excites strong inertial currents in the mixed layer, which radiate downward as near-inertial internal waves and supply energy to interior diapycnal mixing. They appear as a sharp peak near f in ocean current spectra.