ON THE RESPONSE OF THE OCEAN UPPER LAYER TO SYNOPTIC VARIABILITY OF THE ATMOSPHERE

The response of the ocean upper layer to synoptic atmosphere variability is examined using a nonlocal integral model of the subtropical gyre. Our main goal is the analysis of the nonlinear, nonlocal oceanic response to two typical atmospheric disturbances, which were postulated to be of the same intensity but of opposite sign. Thus, we study the nonlinear effects in the response of a horizontally inhomogeneous ocean to synoptic disturbances in the subtropical gyre. It was shown that synoptic atmospheric variability generates an oceanic response which may have climatic consequences. Synoptic upper mixed layer (UML) thermal anomalies reach about 1-2-degrees-C over an area of more than 1000 km x 1000 km, and influence directly the large-scale atmosphere-ocean interaction. This influence is comparatively short term. On the other hand, a series of storms may influence the thermal regime of the whole baroclinic layer. This leads to long-term climatic consequences. Therefore, the simulation of such fluctuations in large-scale models of atmosphere-ocean interaction is necessary. Oceanic horizontal inhomogeneity is most important in the integral heat, momentum and kinetic energy turbulence (KET) balances of the UML after the passage of storms. The effect of oceanic inhomogeneity is at a maximum in the storm-induced frontal zone and is shown particularly in the advective h variations (h is the UML thickness), which are of the same order as the local h variations, as well as in generation of the gradient currents/gradient advection, which are of the same order as the drift currents/drift advection (but slightly less). Obviously, drift advection is the main effect of the UML horizontal inhomogeneity. During the action of strong winds, the heat, momentum and KET balances of the mid-ocean UML are approximately one-dimensional for most of the storm track. During this period, the synoptic vertical motions at the base of the UML must also be considered. Vertical thermal storm-induced advection in the main thermocline exceeds the vertical diffusion by one and a half orders, and may strongly influence the thermal regime of the main thermocline if there are several storms of the same sign and trajectory.