Seasonal variation and governing dynamics of the mixed layer in the Indian Sector of the Southern Ocean
Seasonal variation and governing dynamics of the mixed layer in the Indian Sector of the Southern Ocean
复制标题
南大洋印度区混合层的季节变化及控制动态
DOI：
10.1029/2021jc017838
复制
发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Y.
中科院分区：
文献类型：
--
作者：
Ferreira Azevedo;M.;Aoki;S.;Kitade;Y.
利用2012年1月15日至12月19日期间部署在60°S和140°E的迷你三角跨大洋浮标网的多普勒海流剖面仪和电导率温度深度数据，以及水文模型、再分析输出和卫星图像，研究了南大洋印度洋-太平洋区域上层温度、盐度和密度分布的变化动态。光谱分析证实，近惯性内波是将能量向下传递到混合层（ML）下边界的主要因素，在分析的事件中，有12.5 J m−3或平均表面能的45%能够达到比ML深度更深的深度。在从海洋表面到大气的净热损失期间，大部分能量集中在最大切变层以下，大约80米深度。发现内波事件与标量扩散率增加有关，其幅度可达两个数量级。箱形模式表明，地表冷却在冬季混合地表水中起着最重要的作用，但不足以解释100 m深度以下的变率，在100 m深度以下，水平平流和涡旋增强在调节暖水通量方面也很重要。我们的研究结果阐明了风能如何增强混合，即使是在冰层覆盖的地区，同时影响深度比以前想象的要大。
The dynamics involved in the variability of temperature, salinity, and density distributions in the upper layer of the Indo‐Pacific sector of the Southern Ocean were studied using Acoustic Doppler Current Profiler and Conductivity Temperature Depth data from a mini triangle trans‐ocean buoy network mooring deployed at 60°S and 140°E between January 15th and 19th December 2012, together with hydrographic casts, reanalysis outputs, and satellite imagery. Spectral analysis confirmed that near‐inertial internal waves are a major factor transporting energy downward to the lower boundary of the mixed layer (ML), with 12.5 J m−3or 45% of the mean surface energy being able to reach deeper than the ML depth during one of the analyzed events. During a period of net heat loss from the ocean surface to the atmosphere, most of the energy was concentrated below the maximum shear layer, at around 80 m depth. Internal wave events were found to be linked to scalar diffusivity increases of up to two orders of magnitude. A box model clarified that surface cooling plays the most significant role in mixing surface waters during winter, but it is not enough to explain variability below 100 m depth, where horizontal advection and eddy enhancement are also important in modulating warm water flux. Our results elucidate how wind energy might enhance mixing, even in ice‐covered regions, while influencing depths greater than previously thought.