Intensifying stratified turbulence and mixing towards the oceanic submesoscale front

IF 8.5 1区地球科学 Q1 METEOROLOGY & ATMOSPHERIC SCIENCES

npj Climate and Atmospheric Science Pub Date : 2025-05-12 DOI:10.1038/s41612-025-01069-x

Qunshu Tang, Jianmin Lin, Wen Xu, Zhiyou Jing, Vincent C. H. Tong

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Abstract

The role of submesoscale processes as the primary energy source for ocean turbulence remains controversial due to observational limitations. Seismic imaging captures multi-scale processes from mesoscale to finescale, allowing us to infer turbulence processes. This study identified hundreds of ~200-m-long high seismic reflection patches, primarily caused by vertical temperature changes, moving at 0.24 ± 0.13 m/s across the deep-reaching front of Bransfield Current, Antarctica. Patch distribution within the main current is uneven, increasing exponentially towards the frontal leading edge. Over 95% of the detected patches are concentrated within 10 km from the frontal leading edge, where elevated Thorpe-scale diffusivity exceeding 10⁻² m²/s has been observed hydrographically. These patches may indicate stratified turbulence, including broken internal wave segments, interleaving interfaces, and overturns, which may correspond to wave breaking, frontal instability, and shear instability, respectively. Our findings challenge the recently questioned classical hypothesis that energy cascades directly from internal waves to isotropic turbulence, instead supporting the paradigm of a stratified turbulence stage.

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面向海洋亚中尺度锋的层状湍流和混合增强

由于观测的限制，亚中尺度过程作为海洋湍流主要能量源的作用仍然存在争议。地震成像捕获从中尺度到精细尺度的多尺度过程，使我们能够推断湍流过程。本研究确定了数百个~200米长的高地震反射斑块，主要是由垂直温度变化引起的，以0.24±0.13 m/s的速度在南极洲布兰斯菲尔德洋流的深层前沿移动。主流内的斑块分布不均匀，向锋面前缘呈指数增长。超过95%的检测到的斑块集中在锋面前缘10 km范围内，在这些区域已观测到索普尺度扩散系数升高，超过10−2 m2/s。这些斑块可能表明分层湍流，包括破碎的内波段、交错的界面和倾覆，这可能分别对应于波浪破碎、锋面不稳定和剪切不稳定。我们的发现挑战了最近被质疑的经典假设，即能量直接从内波级联到各向同性湍流，而不是支持分层湍流阶段的范式。

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来源期刊

npj Climate and Atmospheric Science Earth and Planetary Sciences-Atmospheric Science

CiteScore

8.80

自引率

3.30%

发文量

审稿时长

21 weeks

期刊介绍： npj Climate and Atmospheric Science is an open-access journal encompassing the relevant physical, chemical, and biological aspects of atmospheric and climate science. The journal places particular emphasis on regional studies that unveil new insights into specific localities, including examinations of local atmospheric composition, such as aerosols. The range of topics covered by the journal includes climate dynamics, climate variability, weather and climate prediction, climate change, ocean dynamics, weather extremes, air pollution, atmospheric chemistry (including aerosols), the hydrological cycle, and atmosphere–ocean and atmosphere–land interactions. The journal welcomes studies employing a diverse array of methods, including numerical and statistical modeling, the development and application of in situ observational techniques, remote sensing, and the development or evaluation of new reanalyses.