Intense upper ocean mixing due to large aggregations of spawning fish
Intense upper ocean mixing due to large aggregations of spawning fish
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DOI：
10.1038/s41561-022-00916-3
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发表时间：
2022-04
影响因子：
18.3
通讯作者：
Bieito Fernández Castro;Marian Peña;E. Nogueira;M. Gilcoto;Esperanza Broullón;A. Comesaña;D. Bouffard;A. N. Naveira Garabato;B. Mouriño‐Carballido
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作者：
Bieito Fernández Castro;Marian Peña;E. Nogueira;M. Gilcoto;Esperanza Broullón;A. Comesaña;D. Bouffard;A. N. Naveira Garabato;B. Mouriño‐Carballido
小尺度湍流混合在形成海洋环流和广泛的物理和地球化学过程中发挥着关键作用。尽管我们对造成这种混合的地球物理过程的理解有了进步，但生物混合（海洋生物群引起的湍流混合）的性质和重要性仍然存在争议。不确定性的一个主要来源涉及生物混合的效率（通过游泳产生的湍流能量中用于垂直混合海洋的部分），现有的几个现场观测表明其远低于地球物理湍流。在这里，我们揭示了这个问题，通过分析14天的连续测量厘米级湍流在沿海上升流的区域。我们发现，由于产卵季节定期聚集的大规模聚集体的游泳活动，湍流耗散在调查的每个晚上都增加了10到100倍（达到10−6-10− 5 W kg−1）。湍流混合与耗散同时发生，其效率与地球物理湍流相当。我们的研究结果表明，生物驱动的湍流可以是一个非常有效的混合剂，并呼吁重新审视其对生产上层海洋区域的影响。
Small-scale turbulent mixing plays a pivotal role in shaping ocean circulation and a broad range of physical and biogeochemical processes. Despite advances in our understanding of the geophysical processes responsible for this mixing, the nature and importance of biomixing—turbulent mixing caused by marine biota—are still debated. A major source of uncertainty pertains to the efficiency of biomixing (the fraction of the turbulent energy produced through swimming that is spent in mixing the ocean vertically), which the few in situ observations available suggest to be much lower than that of geophysical turbulence. Here we shed light on this problem by analysing 14 days of continuous measurements of centimetre-scale turbulence in an area of coastal upwelling. We show that turbulent dissipation is elevated 10- to 100-fold (reaching 10−6–10−5W kg−1) every night of the survey due to the swimming activity of large aggregations of anchovies that gather regularly over the spawning season. Turbulent mixing is invigorated concurrently with dissipation, and occurs with an efficiency comparable to that of geophysical turbulence. Our results demonstrate that biologically driven turbulence can be a highly effective mixing agent, and call for a re-examination of its impacts on productive upper ocean regions.