On the Possible Frontogenetic Role of Salt Finger Convection in the Ocean

The fundamental problem of studying oceanic fronts is to find the mechanisms that play an essential role in the generation of planetary-scale fronts (frontogenesis) and to maintain them. To study this problem with regard to the North Atlantic Ocean, the fields of horizontal temperature (and salinity) gradients in the intermediate water column have been compared for the first time to the field of the density ratio that characterizes the spatial inhomogeneity of vertical heat and mass transfer due to double diffusion heat and salt processes. The comparison shows the presence of more or less sharp thermohaline frontal zones throughout the periphery of two vast areas in the subtropical and tropical zones covered by intense differential-diffusion convection in the salt finger regime. This is a strong argument that this previously ignored small-scale (experiencing the impact of molecular processes) convection may be a prime cause of large-scale frontogenesis in the oceanic water column.