Sharp frontal interfaces in the near-surface layer of the tropical ocean

Abstract

The small-scale structure of oceanic fronts contains important information about horizontal and vertical exchange of properties in the upper ocean. The data obtained in the western equatorial Pacific warm pool during Tropical Ocean–Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE) and Tropical Ocean Climate Study (TOCS) suggest that the sharp frontal interfaces occasionally observed in the upper layer of the tropical ocean may be associated with gravity currents. These gravity currents originate from the surface pools of relatively low-density (fresh and/or warm) water produced by convective rainfalls and spatially variable diurnal warming. It has been shown that frontal interfaces of less than 100 m width may interact with wind stress via the mechanism of Stommel's “overturning gate.” The anisotropy of sharp frontal interfaces with respect to the wind stress direction can be predicted with a simple nonlinear model including both dissipation and dispersion effects. This study elucidates the role of fronts in the dynamics of the tropical ocean and provides important details to the description of how the temperature–salinity relationship and barrier layer in the warm pool areas are formed.