An estimate of the gas transfer rate from oceanic bubbles derived from multibeam sonar observations of a ship wake
An estimate of the gas transfer rate from oceanic bubbles derived from multibeam sonar observations of a ship wake
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DOI：
10.1029/2004jc002666
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发表时间：
2005-04-13
影响因子：
3.6
通讯作者：
Bradley, DL
中科院分区：
文献类型：
--
作者：
Weber, TC;Lyons, AP;Bradley, DL
实验室已经对气泡的气体传输速率进行了测量，但很难推断到海洋气泡，因为海洋气泡中抑制气体传输的表面活性剂和颗粒物质的数量是不同的。由于未知的气泡产生速率，海上测量变得复杂，这使得难以唯一地识别和观察单个气泡云的演变。消除这些困难的一种方法是测量船舶尾流中的气泡，其中任何给定位置的气泡产生仅限于经过船舶的持续时间。该方法假设减缓自然产生的气泡的气体溶解的机制以类似于减缓船尾流中的气泡溶解的方式起作用。这里报告了使用这种方法测量海洋气泡的气体传输速率。高频上视多波束回声测深仪用于测量双螺旋 61 米研究船尾迹中气泡的空间分布。从多波束数据中提取水动力强迫函数，并将其用于气泡云演化模型，其中气体传输速率被视为自由参数。将对应于不同气体传输速率的模型运行的输出与数据中观察到的随时间变化的尾流深度进行比较。结果表明模型和数据之间的一致性表明，为了解释气泡在尾流中的持久性，气体传输速率必须比不含表面活性剂的气泡低大约 15 倍。
Measurements of gas transfer rates from bubbles have been made in the laboratory, but these are difficult to extrapolate to oceanic bubbles where populations of surfactants and particulate matter that inhibit gas transfer are different. Measurements at sea are complicated by unknown bubble creation rates that make it difficult to uniquely identify and observe the evolution of individual bubble clouds. One method that eliminates these difficulties is to measure bubbles in a ship wake where bubble creation at any given location is confined to the duration of the passing ship. This method assumes that the mechanisms slowing the gas dissolution of naturally created bubbles act in a similar manner to slow the dissolution of bubbles in a ship wake. A measurement of the gas transfer rate for oceanic bubbles using this method is reported here. A high-frequency upward-looking multibeam echosounder was used to measure the spatial distribution of bubbles in the wake of a twin screw 61-m research vessel. Hydrodynamic forcing functions are extracted from the multibeam data and used in a bubble cloud evolution model in which the gas transfer rate is treated as a free parameter. The output of model runs corresponding to different gas transfer rates is compared to the time-dependent wake depth observed in the data. Results indicating agreement between the model and the data show that the gas transfer rate must be approximately 15 times less then it would be for surfactant-free bubbles in order to explain the bubble persistence in the wake.