ON MIDOCEAN FRONTS IN MULTILAYER MODELS

A theory of the general circulation which admits mid-ocean fronts is e xamined. This study is related to some earlier studies of two layer pl anetary geostrophic systems, where it was argued that interior discont inuities, or ''fronts'', generally arise as a result of the nonlineari ty in the continuity equation. Similar dynamics are studied here under more general circumstances. It is argued that the most general soluti on for the interior thermocline requires several fronts, each of which arises in response to a mismatch of subsurface potential vorticity st ructure on isopycnals. Further, these fronts can influence each other and determine large areas of the basin scale potential vorticity field . Comparisons between special analytical solutions and numerical solut ions are made. The main result of this work is that the frontogenisis in planetary geostrophic dynamics is robust, characteristic of highly stratified systems and of potential importance to basin scale structur e.