Vertical velocities at an ocean front

Simple scaling arguments conclude that the dominant motions in the ocean ar e horizontal. However, the vertical velocity plays a crucial role, connecti ng the active upper layer with the deep ocean. Vertical velocities are most ly associated with the existence of non-transient atmospheric wind forcing or with the presence of mesoscale features. The former are the well known u pwelling areas, usually found at the eastern side of the oceans and charact erised by upward vertical velocities. The latter have been observed more re cently in a number of areas of the world's oceans, where the vertical veloc ity has been found to be of the order of several tens of meters per day, th at is, an order of magnitude higher than the largest vertical velocity usua lly observed in upwelling areas. Nevertheless, at present, vertical velocit ies cannot be measured and indirect methods are therefore needed to estimat e them. In this paper, the vertical velocity field is inferred via the quas igeostrophic omega equation, using density data from a quasi-permanent uppe r ocean front located at the northern part of the western Alboran gyre.