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首页> 外文期刊>Estuarine Coastal and Shelf Science >Internal wave mixing in warming lake Grevelingen
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Internal wave mixing in warming lake Grevelingen

机译：格雷韦林根湖内的内波混合

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Seasonal hypoxia or even anoxia can occur in some local deep basins of coastal waters. Such low summertime oxygen contents especially affect benthic life. The seasonal coastal hypoxia is commonly related to biological increased respiration and to physical limited vertical turbulent exchange that is associated with increased vertical stable density stratification. However, the same stratification can support internal waves that may break and locally generate turbulence. Here, we investigate the physics of internal wave motions in saltwater Lake Grevelingen (SW-Netherlands) during warming in mid-spring. Grevelingen is refreshed by weak tidal motions through an open sluice in its dam to the North Sea. The outer North Sea has a surface tidal range of about 3 m, but the lake surface tidal range is negligible ( 0.1 m). To quantify vertical turbulent exchange, high-resolution temperature sensors were moored in conjunction with a current meter in 36 m water depth for three days. The site is known for anoxic conditions near the bottom in summer. While a 3-day, 30-m mean eddy diffusivity of [K-z] = 4 +/- 2 x 10(-5) m(2) s(-1) is found, the overall mean turbulence dissipation rate (turbulent flux) is [epsilon] = 1.1 +/- 0.6 x 10(-7) m(2) s(-3). Turbulent mixing occurs episodically, via near-surface cooling during night and increased winds, via sparse shear-driven breaking of internal waves at the main pycnocline, and via sheared near-bottom currents. Shear-driven turbulence is not commonly found in fresh-water lakes. Just below the main pycnocline around mid-depth a layer of weak turbulence is observed, as in fresh-water lakes. The observed turbulent exchange is sufficient to warm the near-bottom waters over the course of summer, but insufficient to prevent the biology from over-consuming oxygen contents.
机译：在沿海水域的某些局部深盆地中，可能会发生季节性缺氧甚至缺氧。如此低的夏季氧气含量尤其会影响底栖生物的寿命。季节性沿海缺氧通常与生物呼吸增加和与垂直稳定密度分层增加相关的有限的垂直湍流交换有关。但是，相同的分层可以支持可能破裂并局部产生湍流的内部波。在这里，我们研究了春季中期变暖期间盐水湖格里维林根（西南荷兰）内波运动的物理学。格雷夫林根的潮汐微弱，通过其通往北海的水坝中的一条敞开的闸门使人耳目一新。北海外部的潮汐范围约为3 m，但湖泊的潮汐范围可以忽略不计（<0.1 m）。为了量化垂直湍流交换，将高分辨率温度传感器与电流表一起停泊在水深36 m的区域中，持续三天。该地点以夏季底部附近的缺氧条件而闻名。虽然发现<[Kz]> = 4 +/- 2 x 10（-5）m（2）s（-1）的3天30米平均涡流扩散率，但总体平均湍流耗散率（湍流通量）＜ε＞ ＝ 1.1 +/- 0.6×10（-7）m（2）s（-3）。湍流混合通常是通过夜间的近地表降温和增加的风，稀疏的剪切驱动的主旋律内波的破碎驱动破裂以及剪切的近底电流发生的。剪切驱动的湍流在淡水湖中并不常见。就像在淡水湖中一样，在中深度附近的主要比诺克林之下，观察到了微弱的湍流。所观察到的湍流交换足以在整个夏季加热近乎底部的水域，但不足以防止生物学过度消耗氧气。

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