PDF(Pubmed)
Abstract：
Turbulent mixing in the ocean exerts an important control on the rate and structure of the overturning circulation. However, the balance of processes underpinning this mixing is subject to significant uncertainties, limiting our understanding of the overturning\'s deep upwelling limb. Here, we investigate the hitherto primarily neglected role of tens of thousands of seamounts in sustaining deep-ocean upwelling. Dynamical theory indicates that seamounts may stir and mix deep waters by generating lee waves and topographic wake vortices. At low latitudes, stirring and mixing are predicted to be enhanced by a layered vortex regime in the wakes. Using three realistic regional simulations spanning equatorial to middle latitudes, we show that layered wake vortices and elevated mixing are widespread around seamounts. We identify scalings that relate mixing rate within seamount wakes to topographic and hydrographic parameters. We then apply such scalings to a global seamount dataset and an ocean climatology to show that seamount-generated mixing makes an important contribution to the upwelling of deep waters. Our work thus brings seamounts to the fore of the deep-ocean mixing problem and urges observational, theoretical, and modeling efforts toward incorporating the seamounts\' mixing effects in conceptual and numerical ocean circulation models.
摘要：
海洋中的湍流混合对翻转环流的速率和结构具有重要的控制作用。然而,支撑这种混合的过程的平衡存在显著的不确定性，限制了我们对倾覆的深层上升肢体的理解。这里,我们调查了迄今为止主要被忽略的数万个海山在维持深海上升流方面的作用。动力学理论表明，海山可以通过产生背波和地形尾流涡旋来搅拌和混合深水。在低纬度，搅拌和混合预计将通过尾流中的分层涡旋机制增强。使用跨越赤道到中纬度的三个现实区域模拟，我们表明，层状尾流涡旋和高度混合在海山周围很普遍。我们确定了将海山尾流中的混合速率与地形和水文参数相关联的缩放。然后，我们将这种缩放方法应用于全球海山数据集和海洋气候学，以表明海山产生的混合对深水的上升做出了重要贡献。因此，我们的工作将海山带到了深海混合问题的面前，并敦促进行观测，理论,以及在概念和数值海洋环流模型中纳入海山混合效应的建模工作。
