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全球内波混合的时空分布特征
Spatial and temporal characteristic of global internal wave-induced mixing
为了揭示全球海域内波混合的时空分布规律并探究其影响因素,本文采用内波细尺度参数化方法统计分析了2006—2021年全球250~500 m深度段的Argo温、盐数据,得到内波混合的时空分布特征以及全球海域在不同季节下风生近惯性能通量对内波混合的影响规律。在空间上,北大西洋和南大洋全年都存在较大的风生近惯性能通量,从而产生较强的内波混合;在西太平洋和40°N以北的北太平洋,内波混合与风生近惯性能通量的空间分布不一致,与涡动能的空间分布一致,说明内波混合不仅会受到风生近惯性能通量的影响,可能还会受到涡旋的调控。在时间上,12—2月全球内波混合最强,其次是9—11月和3—5月,6—8月最弱,这与全球风生近惯性能通量的季节变化相一致。在北半球,冬季的风生近惯性能通量和内波混合最大,而夏季风生近惯性能通量和内波混合最小。在南半球,风生近惯性能通量和内波混合四个季节的变化不一致。南、北半球内波混合和风生近惯性能通量的季节循环大致吻合,尤其在北大西洋,风生近惯性能通量和内波混合吻合较好。
To reveal the spatial and temporal distribution patterns of internal wave-induced mixing in global ocean and investigate its influencing factors, this study employs an internal wave fine-scale parameterization method to statistically analyze Argo temperature and salinity data at 250-500 m depth from 2006 to 2021. The analysis characterizes the spatial and temporal features of internal wave mixing and identifies the impact of wind-induced near-inertial energy flux on mixing across global oceans under varying seasonal conditions. In space, there is strong wind-induced near-inertial energy flux in the four seasons of the North Atlantic and Southern Ocean in the whole year, resulting in significant internal wave mixing. However, in the western Pacific and the north of 40°N in the North Pacific, the spatial distribution of internal wave-induced mixing are inconsistent with the wind-induced near-inertial energy flux. Instead, it follows the spatial distribution of eddy kinetic energy since internal wave-driven mixing can be also regulated by eddies. In terms of time, the strongest internal wave-induced mixing of global occurs from December to February, followed by September to November and March to May, and June to August. This is consistent with the seasonal variation of global wind-induced near-inertial energy flux. In the northern hemisphere, the wind-induced near-inertial energy flux and mixing are the strongest in winter, while the weakest in summer. In the southern hemisphere, the variation of wind-induced near-inertial energy flux and mixing over four seasons is inconsistent. However, the seasonal cycles of mixing and wind-induced near-inertial energy flux in the northern and southern hemispheres are roughly consistent, especially in the North Atlantic, where the wind-induced near-inertial energy flux and mixing match well.
内波混合 / 扩散率 / 耗散率 / 风生近惯性能通量 / 涡动能 / 细尺度参数化 / Argo / 全球
internal wave-induced mixing / diffusivity / dissipation rate / wind-induced near-inertial energy flux / eddy kinetic energy / fine-scale parameterization / Argo / global
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We review the physics of near-inertial waves (NIWs) in the ocean and the observations, theory, and models that have provided our present knowledge. NIWs appear nearly everywhere in the ocean as a spectral peak at and just above the local inertial period f, and the longest vertical wavelengths can propagate at least hundreds of kilometers toward the equator from their source regions; shorter vertical wavelengths do not travel as far and do not contain as much energy, but lead to turbulent mixing owing to their high shear. NIWs are generated by a variety of mechanisms, including the wind, nonlinear interactions with waves of other frequencies, lee waves over bottom topography, and geostrophic adjustment; the partition among these is not known, although the wind is likely the most important. NIWs likely interact strongly with mesoscale and submesoscale motions, in ways that are just beginning to be understood.
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