Bottom Boundary Layer Turbulence and Abyssal Recipes (BLT Recipes)

底部边界层湍流和深渊配方（BLT 配方）

• 批准号: NE/S001433/1
• 负责人: Alberto Naveira Garabato
• 金额: $ 113.26万
• 依托单位: University of Southampton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FS001433%2F1
• 关键词: Bottom; Boundary; Layer; Turbulence; Abyssal

Since the seminal work of Walter Munk in the 1960s, oceanographers have believed that the upwelling of cold, abyssal waters that regulates the deep ocean's ability to sequester heat and carbon for decades to millennia (thereby shaping Earth's climate) is driven by centimetre-scale turbulent mixing associated with breaking waves in the ocean interior. Measurements of deep-ocean turbulence over the last two decades, however, starkly contest this scenario, and instead suggest that mixing by breaking waves drives *downwelling* of abyssal waters. Inspired by this conundrum, recent theoretical investigations have developed a tantalising alternative view of the role of mixing in sustaining deep-ocean upwelling. In this new view, upwelling is driven by highly localised turbulence within thin (typically tens of metres thick) layers near the seafloor, known collectively as the bottom boundary layer.In this proposal, we set out to assess the validity of this new paradigm, and figure out how it works, by obtaining the first set of concurrent, systematic measurements of (1) large-scale mixing and upwelling, (2) their interior and bottom boundary layer contributions, and (3) the processes underpinning these contributions, in a representative deep-ocean basin (the Rockall Trough, in the Northeast Atlantic). To this end, we will conduct a year-long field programme involving three research cruises, in close collaboration with a group of U.S. project partners.To measure (1), in the first cruise we will release a long-lived chemical tracer detectable at very low concentrations near the seafloor on the basin's eastern flank, where deep waters flow into the basin from the south. We will monitor how the tracer mixes and upwells as it fills the basin by sampling it at 6 and 12 months after its release, during the two subsequent cruises. To measure (2) and (3), we will adopt a two-pronged approach. First, we will assess mixing and upwelling in the ocean interior and the transition into the bottom boundary layer by deploying turbulence-measuring profilers at hundreds of sites throughout the basin, in the first and third cruises. Second, as these ship-deployed profilers are unsuitable to approach the seafloor closely, we will obtain targeted measurements of mixing and upwelling across the bottom boundary layer in two ways: (i) by conducting two 6-month-long deployments of a cluster of novel, turbulence-measuring instruments moored at the seafloor, at two sites on the basin's sloping boundary; and (ii) by performing a near-bottom release of a short-lived dye at each of the mooring deployment sites, and monitoring how the dye mixes and upwells over several days after its release.We will integrate our measurements of (1)-(3) into the design of a realistic numerical model of the circulation in the Rockall Trough, and use the model to conduct a rigorous, quantitative test of the new paradigm of ocean mixing. We expect this test to provide the first evidence of the dominance of bottom boundary layer turbulence in driving deep-ocean upwelling and, in so doing, trigger a profound transformation in our understanding and modelling of deep-ocean circulation.

自从沃尔特·穆克（Walter Munk）在1960年代的开创性工作以来，海洋学家认为，寒冷的，深渊水域的上升流动，这些水调节了深海数十年来隔离高温和碳的能力（从而塑造了地球的气候）是由厘米刻度的cale式的，与海洋中的破坏性波动相关。然而，在过去的二十年中，深海洋湍流的测量很明显，反而暗示着通过破坏浪潮驱动 *倒塌的河水的混合。受这个难题的启发，最近的理论研究已经对混合在维持深度海洋上升流中的作用的作用产生了诱人的替代观点。在这种新的观点中，上升流是由在海底附近薄（通常是数十米厚）内的高度定位的湍流驱动的，集体称为底部边界层。在这项建议中，我们着手评估这种新范式的有效性，并通过获得第一组相关的（沿着端的杂物）（1）大小（1）的（1）相关的（1）层次（1）层次的（1）层次（1）层次（1），并弄清楚它的有效性（1）。贡献，以及（3）在代表性深海盆地（东北大西洋的Rockall槽）中所采取的这些贡献的过程。为此，我们将与一组美国项目合作伙伴密切合作进行为期一年的现场计划。测量（1），在第一次巡游中，我们将在盆地东部侧面的海底附近释放一个长寿命的化学示踪剂，可在非常低的浓度下检测到，那里的深水流入南部的水域。我们将通过在随后的两个巡游中在释放后6和12个月对盆地进行采样，以调查示踪剂在填充盆地时如何混合和上升。为了衡量（2）和（3），我们将采用两管齐下的方法。首先，我们将通过在第一和第三巡航中部署数百个地点的湍流测量分配者来评估海洋内部的混合和上升流以及向底部边界层的过渡。其次，由于这些被船只部署的牧师不适合紧密接近海底，我们将通过两种方式获得对底部边界层的混合和向上移动的有针对性的测量：（i）通过在海上有两个新颖的，湍流的乐器上的新颖，湍流的乐器，在两个基础上，在两个基础上，在两个基础上进行了底层底层的底座，均在底座上进行了底层; （ii）通过在每个系泊部部部署地点进行短寿命的染料释放，并监视染料释放后的几天内如何混合和上升。我们将整合我们（1） - （3）的测量值，以将岩石循环的循环量的型号进行了测试，并使用型号进行了良好的测试。我们预计该测试将提供第一个证据，证明底部边界层湍流在驱动深cean上升流中的主导地位，并且在这样做时，触发了我们对深向海洋循环的理解和建模的深刻转变。

项目成果

Sensitivity of Deep Ocean Mixing to Local Internal Tide Breaking and Mixing Efficiency

• DOI: 10.1029/2019gl085056
• 发表时间: 2019-12
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: L. Cimoli;Colm‐cille P. Caulfield;H. Johnson;D. Marshall;A. Mashayek;A. N. Naveira Garabato;C. Vic

Surface factors controlling the volume of accumulated Labrador Sea Water

控制拉布拉多海水积聚量的地表因素

• DOI: 10.5194/egusphere-2023-1564
• 发表时间: 2023
• 作者: Kostov Y