Towards a theory of the abyssal circulation

海洋环流最深处的一幅经过修正的图景正在浮现。在粗糙的地形上，为减轻密集的底层沃茨并使其上升到中等深度所需的混合作用大大增强。这个项目将致力于一个动态的理论，捕捉边界转换和内部流动和分层之间的相互作用。这项工作很重要，因为深海有能力储存大量的热量和碳。更全面地了解是什么动力学过程塑造了它的环流，将有助于气候模型捕捉它在不断变化的气候中的行为和作用。在解释冰河时期大气中二氧化碳的减少方面，深渊起到了关键作用。更深入地了解深海环流的动态也将有助于更好地了解它在地球历史的这些时期和其他时期可能有何不同，拟议的工作将建立一个深海环流对斜坡上海底强化混合反应的动力学模型层次，重点是地形斜坡上边界层与深渊内部边界层之间的双向相互作用。这种相互作用将用边界层理论明确地表示出来。该方法将从斜坡上的局部一维动力学开始，然后在简单的二维示例中考虑它们与大规模背景的耦合，随后扩展到理想化和越来越现实的三维设置。这将把最近关于斜坡上海底强化混合的工作与基于平底和垂直侧壁的海洋盆地的深海翻转比例理论联系起来。这些动力学将使用行星地转模型进行探索，其简化动力学允许直接的动力学洞察和控制数值解，解决所有特征，包括地形斜坡上所有重要的边界层。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

A revised picture is emerging of the deepest portion of the ocean's circulation. The mixing required to lighten dense bottom waters and that allows them to rise to mid-depth is strongly enhanced over rough topography. This project will work toward a dynamical theory that captures the interplay between the boundary transformations and interior flows and stratification. This work is important because the abyssal ocean has the capacity to store vast amounts of heat and carbon. A more complete understanding of what dynamical processes shape its circulation will help climate models capture its behavior and role in a changing climate. A pivotal role has been ascribed to the abyss in explaining the drawdown of atmospheric carbon dioxide during ice ages. Deeper insight into the dynamics of the abyssal circulation will also help understand better how it may have been different during these and other periods of Earth's history.The proposed work will build a hierarchy of dynamical models of the response of the abyssal circulation to bottom-intensified mixing on slopes with a focus on the two-way interaction between boundary layers on topographic slopes and the interior of the abyss. This interaction will be expressed explicitly using boundary layer theory. The approach will start with the local one-dimensional dynamics on slopes, then consider their coupling to the large-scale context in simple two-dimensional examples, and subsequently extend to idealized and increasingly realistic three-dimensional setups. This will connect recent work on bottom-intensified mixing on slopes to scaling theories for the abyssal overturning that are based on ocean basins with a flat bottom and vertical sidewalls. These dynamics will be explored using a planetary geostrophic model, whose reduced dynamics allow for direct dynamical insight and controlled numerical solutions that resolve all features, including the all-important boundary layers on topographic slopes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.