Surface effects due to subsurface processes: A survey

This report surveys the oceanic subsurface dynamic processes which have signatures on the ocean surface. These surface effects can appear in the form of changes in both surface current distributions and local wave structures (or profiles). Based upon their physical scales, these effects are classified into phenomena produced by mechanisms associated with weak and strong interactions. Two types of phenomena are distinct among surface wave weak interactions: (1) broad band phenomena--includes wave-wave energy transfer and general wave train instability; and (2) narrow band phenomena--includes Benjamin-Feir instability, recurrence, and envelope solutions. All these phenomena share the following physical characteristics: (1) they may be manifested only by the long dominant waves in a wave field and yet the behavior of short waves is determined by the strong interactions with the long waves rather than by these processes; and (2) they are evolutionary phenomena with a time scale of 1/(ak) sq times the wave period where a is the wave amplitude and k is the wave number of the dominant wave. The strong interactions are those phenomena whose time scale is of the order of the wave period and space scale is of the order of the wavelength. Detailed wave structures (or profiles) are the prime sources of information. Strong interactions include the strong Longuet-Higgins instability, wave-current interactions, long wave-short wave interactions, and the processes of parasitic capillary formation and microscale breaking induced by surface and drift.