INTERGYRE COMMUNICATION IN A 3-LAYER MODEL

A three-layer, wind-driven, general circulation model involving both s ubtropical and subpolar gyres has been developed to study intergyre ex change. Following some early studies, the present work allows flow to baroclinically cross the intergyre boundary. This model differs from p ast work by examining a three-layer fluid. Solutions with both southwa rd and northward subsurface flows are obtained. The two principal obje ctives of this work are to clarify the structure and maintenance of th e permanent thermocline and to aid in understanding the distribution o f deep water masses. A class of thermocline structures at the zero Ekm an pumping line has been constructed that permits intergyre exchange, or communication. The zones of ''change are called windows. In this st udy, the windows have several unique properties relative to those comp uted elsewhere, and exhibit relatively rich structure. Principally, th e addition of an active third layer allows a new second baroclinic win dow to open. This new window is physically and dynamically distinct fr om the first window (found in previous studies), and most of the inter gyre baroclinic transport can occur through it. Its appearance also su pports the conjecture that the number of communication windows increas es with the number of active layers. In addition to the model developm ent, observed potential vorticity distributions have been reexamined w ithin the context of this model. Possible explanations for deep potent ial vorticity contours in the North Atlantic and North Pacific oceans are proposed.