Dynamic Characteristics of a Submesoscale Front and Associated Heat Fluxes Over the Northeastern South China Sea Shelf

Abstract

ABSTRACT Submesoscale fronts, which are ubiquitous phenomena in the ocean, contribute considerably to oceanic material transports and energy cascades because of their ageostrophy. The dynamic characteristics of a thermal front over the northeastern continental shelf of the South China Sea (SCS) in winter are investigated using a two-layer nested high-resolution regional ocean model system. Results show that a strong thermal front is generated over the slope of the SCS area in winter with a cross-front temperature difference of 5°C and a spatial scale of 6 km. The calculated Rossby number reaches O(1) at the front and is accompanied by strong secondary circulation; the vertical velocity can reach 40 m d−1. The calculated barotropic and baroclinic energy conversion reveals that background kinetic and potential energies provide the energy generation of a submesoscale front. Meanwhile, the submesoscale front induces strong horizontal and vertical heat fluxes of up to 8×105 and 1.7×103 W m−2, respectively. The heat flux promotes not only the cross-shelf exchange of heat in the horizontal direction but also the re-stratification of seawater in the vertical direction.