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.

摘要

亚尺度锋是海洋中普遍存在的现象，由于它们的地转现象，对海洋物质运输和能量级联有很大贡献。使用两层嵌套的高分辨率区域海洋模式系统研究了冬季南海东北大陆架 (SCS) 热锋的动力学特征。结果表明，冬季在南海地区的斜坡上产生了一个强烈的热锋，其跨锋温差为5°C，空间尺度为6 km。计算出的Rossby数在锋面达到O (1)，并伴随着较强的二次环流；垂直速度可达40 md ^-1. 计算出的正压和斜压能量转换表明背景动能和势能提供了亚中尺度锋的能量产生。同时，次尺度锋面分别产生高达8×10 ⁵和1.7×10 ³  W m ^{-2 的}强水平和垂直热通量。热通量不仅促进了水平方向的跨架热交换，而且促进了海水在垂直方向的重新分层。