Spatial structure of turbulent mixing inferred from historical CTD datasets in the Indonesian seas
Spatial structure of turbulent mixing inferred from historical CTD datasets in the Indonesian seas
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DOI：
10.1016/j.pocean.2020.102312
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发表时间：
2020-05-01
影响因子：
4.1
通讯作者：
Atmadipoera, Agus S.
中科院分区：
文献类型：
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作者：
Purwandana, Adi;Cuypers, Yannis;Atmadipoera, Agus S.
印度尼西亚海域的湍流动能耗散率和垂直扩散率是根据印度尼西亚和国际游轮首次收集的CTD历史测量数据推断出来的。利用改进的索普尺度法从CTD中推断出耗散率，并与微观结构测量结果进行了验证。在海峡、狭窄通道和浅地形等产生内潮和印度尼西亚式通流（ITF）强烈的地方，近场站观测到类似于[10(-6)-10(-7)]m(2) s（-3）的耗散率升高，而远场站和斜斜以下观测到类似于[10(-8)-10(-10)]m(2) s（-3）的耗散率较低。主要混合热点位于ITF西线的Labani海峡和Dewakang水域的浅水地形，即通过苏拉威西海、望加锡海峡和弗洛雷斯海连接北太平洋源头的通道；在Halmahera、Lifamatola和Buru海峡为ITF的东线，即通过Halmahera海、Maluku海、Seram海连接南太平洋源头的通道；及在创新科技基金出口通道，即龙目岛、沙普海峡及Ombai海峡。东线比西线耗散更大，这与东线对太平洋海域盐度峰值的侵蚀更强是一致的。我们发现潮汐的变化影响了耗散率和扩散率，这是由yoyo剖面数据集得出的结论。Nagai和Hibiya（2015）的高分辨率三维水动力模型输出推断的耗散率的空间格局与混合热点位置的观测结果基本一致，表明M-2内潮是驱动印尼海域湍流动能耗散率的主导因素。然而，该模式也显示出斜斜较低耗散率的倾向，我们将其归因于缺乏对ITF和中尺度环流的代表，以及弱混合区较高耗散率的倾向，这表明对平静水域背景耗散率的高估。
Turbulent kinetic energy dissipation rates and vertical diffusivities in the Indonesian seas are inferred from historical CTD measurements gathering for the first time data from Indonesian and international cruises. Dissipation rates are inferred from the CTD using an improved Thorpe scale method, which is validated against microstructure measurements. Elevated dissipation rates similar to [10(-6)-10(-7)] m(2) s(-3), were observed in the near field stations, such as in the straits, narrowing passages and shallowing topography where internal tides are generated and Indonesian throughflow (ITF) is intense, while lower dissipation rates similar to [10(-8)-10(-10)] m(2) S(-3 )were observed in the far field stations and below the pycnocline. The main mixing hot spots are located in the Labani Channel and shallowing topography of the Dewakang waters for the western route of ITF, i.e. the passage that connects the north Pacific source via Sulawesi Sea, Makassar Strait and Flores Sea; in the straits of Halmahera, Lifamatola, and Buru for the eastern route of ITF, i.e. the passage that connects the south Pacific source via Halmahera Sea, Maluku Sea, Seram Sea; and in the ITF exit passages, i.e. the Lombok, Sape and Ombai Straits. The eastern route is more dissipative than the western route, which is consistent with the stronger erosion of the salinity peak of the Pacific waters along the eastern route. We found that tidal variations influence the dissipation rates and diffusivities as has been suggested from the yoyo profiling datasets. The spatial pattern of dissipation rates inferred from the high-resolution 3D hydrodynamics model output of Nagai and Hibiya (2015) shows a general agreement with the observations in the location of the mixing hot spots and suggests that the M-2 internal tide is the dominant factor driving the turbulent kinetic energy dissipation rates in the Indonesian seas. Yet the model also shows a bias toward lower dissipation rate in the pycnocline, that we attribute to the lack of representation of the ITF and mesoscale circulation and a bias toward higher dissipation rate in the weak mixing region, suggesting an overestimation of the background dissipation rate in calm waters.