Gyroscopic waves in the Mediterranean Sea

Abstract

In the ocean outside areas of dense-water formation, coherent vertical motions (w) are generally much weaker (∼10-3) than horizontal (u, v) ones. According to theoretical models based upon "the traditional approximation", i.e. where the horizontal component of the Coriolis force is neglected, describing inertio-gravity waves in the ocean interior, this holds especially for motions at the inertial frequency f: w(f) < O(10-2 (u(f),v(f))). We present observations of significant w(f), with mean values of 10-1(u(f),v(f)) and occasional values of 1(u(f),v(f)), from the deep Western Mediterranean Sea characterized by very small buoyancy frequency N = 0 ± 0.4f. Our observations also present evidence of vertical propagation of internal waves, originated in the near-surface density stratified layers, through homogeneous layers below. The observations could be interpreted only within the framework of "non-traditional approach" within the horizontal component of the Coriolis force fully taken into account. Copyright 2005 by the American Geophysical Union.