Subduction along a midocean front and the generation of intrathermocline eddies: A theoretical study

Through an idealized model, the authors consider the dynamics of subduction along a midocean front and its linkage to the intrathermocline eddies (ITEs). The subduction is necessitated by advective-diffusive balance of potential vorticity (PV), with its flux mainly a function of the mixed layer depth over the normal range of the horizontal diffusivity. The mismatch of PV impedes the entry of the subducted water into the interior, resulting in an excess flux that peaks at some intermediate mixed layer depth. This mismatch also causes the generation of anticyclonic ITEs, whose radius contains no lower bound, and a maximum limited by the entrainment rate. Through entrainment cooling, ITEs may leave their imprints in the surface temperature, giving rise to a meandering appearance of the front, even in the absence of instability.