The Downwelling Limb of the Thermohaline Circulation

理论价值：最近的观测、理论和模拟研究都表明，温盐环流下流分支的上部集中在侧向边界附近受浮力损失影响的强洋流中。然而，控制海水从上层海洋下沉到中深海和深海的动力学和热力学，以及这些下沉区域对总体环流的影响，还没有得到很好的理解。对于下沉是发生在边界流的空间尺度上，还是发生在较窄的混合驱动的边界层内，如以前的理论所建议的那样，缺乏明确的认识。提出的研究旨在通过高分辨率，非流体静力数值模型计算和实验室实验明确地表示这些下水管区域。拟议研究的科学目标是：i)确定控制横向边界附近下降的速率和空间尺度的因素；ii)检验以往关于下坡边界层的理论模型及其对流域尺度环流的影响；iii)确定是否需要明确解决近边界浮力强迫湍流的细节，以便忠实地反映下流区对盆地尺度环流的影响。更广泛的影响：拟议的研究将对研究和教育活动产生更广泛的影响。拟议研究的科学目标将直接影响我们对温盐环流的平均和低频变率的理解，它在气候系统中的作用，以及我们模拟它的能力。边界附近的混合和下沉过程也影响海洋学的其他分支，如生物学和化学。这项研究的结果也将通过在科学期刊上发表、在国家和国际会议上以及在研讨会上介绍的方式广泛地提供给科学界。两位pi都是联合教育/研究机构的工作人员，他们在其中发挥（并计划继续）教学，建议，监督和培训研究生和暑期学生研究员（本科生）。这项研究也将有助于维持伍兹霍尔海洋研究所地球物理流体动力学实验室作为教学和培训设施。

Intellectual Merit: Recent observational, theoretical, and modeling studies all suggest that the upper part of the downwelling limb of the thermohaline circulation is concentrated in strong currents subject to buoyancy loss near lateral boundaries. Nonetheless, the dynamics and thermodynamics that control where waters sink from the upper ocean to mid- and deep-depths, and what the consequences of these downwelling regions are for the general circulation, are not well understood. There is a lack of clear understanding on whether the downwelling occurs over the spatial scale of the boundary current or within a narrower, mixing-driven, boundary layer, as suggested by previous theories. The proposed study seeks to explicitly represent these downwelling regions in high resolution, non-hydrostatic numerical model calculations and laboratory experiments. The scientific objectives of the proposed study are to: i) To determine what controls the rate and spatial scales of downwelling near lateral boundaries; ii) To test previous theoretical models of downwelling boundary layers and their influence on the basin-scale circulation; iii) To determine if the details of the near-boundary buoyancy-forced turbulence needs to be explicitly resolved in order to faithfully represent the influence of the downwelling regions on the basin-scale circulation Broader Impacts: The proposed study will have broader impacts spanning both research and educational activities. The science objectives of the proposed study will have direct impact on our understanding of the mean and low frequency variability of the thermohaline circulation, its role in the climate system, and our ability to model it. The processes of mixing and downwelling near boundaries also impacts other branches of oceanography such as biology and chemistry. The results of this study will also be made broadly available to the scientific community through publication in scientific journals, presentation at national and international meetings, and in seminars. Both PIs are staff in a joint educational/research institution within which they have played a role (and plan to continue) in teaching, advising, supervising and training graduate students and summer student fellows (undergraduate). This research will also help maintain the Woods Hole Oceanographic Institution Geophysical Fluid Dynamics laboratory as a teaching and training facility.