Submesoscale dynamics in the Bay of Bengal: Inversions and instabilities

High-resolution observations reveal the complex processes controlling the
evolution and subduction of a cold and salty, dense filament in the Bay of
Bengal. The filament, likely formed through coastal upwelling, was
advected offshore by a mesoscale strain field and brought adjacent to
fresher water from runoff and rain. The front on an edge of the dense
filament is observed to undergo restratification and steepening,
responding to evolving mesoscale and submesoscale convergence and
divergences. Measurements and analyses indicate the development of both
small-scale instabilities (such as SI) and slightly larger-scale
ageostrophic secondary circulation, acting in concert to subduct and stir
surface heat into the interior. Our results highlight the importance of
small-scale three-dimensional dynamics in setting upper ocean properties
in the Bay of Bengal.

高分辨率观测揭示了控制孟加拉湾（Bay of Bengal）内冷高盐致密丝状体演化与潜沉的复杂物理过程。该丝状体大概率由沿岸上升流形成，经中尺度应变场平流输送至外海，并与径流及降水带来的低盐水团毗邻。观测显示，致密丝状体边缘的锋面会经历再层化与陡峭化过程，响应于不断演变的中尺度与亚中尺度辐合、辐散运动。测量与分析表明，小尺度不稳定（如SI）与稍大尺度的非地转次级环流共同发展，二者协同将表层热量潜沉并混合至海洋内部。本研究结果凸显了小尺度三维动力过程在塑造孟加拉湾上层海洋特性中的关键作用。