On the role of seamounts in upwelling deep-ocean waters through turbulent mixing

• 成果类型: Article
• 署名作者: Mashayek, Ali; Gula, Jonathan; Baker, Lois E.; Garabato, Alberto C. Naveira; Cimoli, Laura; Riley, James J.; de Lavergne, Casimir
• 署名单位: University of Cambridge; Ifremer; Centre National de la Recherche Scientifique (CNRS); Institut de Recherche pour le Developpement (IRD); Universite de Bretagne Occidentale; Institut Universitaire Europeen de la Mer (IUEM); Institut Universitaire de France; University of Edinburgh; University of Southampton; University of Cambridge; University of Washington; University of Washington Seattle; Centre National de la Recherche Scientifique (CNRS); Sorbonne Universite; Institut de Recherche pour le Developpement (IRD); Museum National d'Histoire Naturelle (MNHN)
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-9307
• DOI: 10.1073/pnas.2322163121
• 发表日期: 2024-07-02
• 关键词: overturning circulation; topography; driven; DISSIPATION; energetics; shear; lee

摘要

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.