Collaborative Research: Transport, Internal Waves and Mixing in the Samoan Passage

智力优势：向北流入北太平洋深海的南极底层水大部分通过萨摩亚航道，使其成为颠覆的太平洋环流的关键瓶颈。详细的海流计和水文观测证实，有6.0斯维尔德鲁普的强劲北流。此外，测量结果还暗示了极强的混合和液压控制。然而，许多重要的问题仍然没有得到解答，包括水流的水力控制程度、混合的强度和导致混合的过程、潮汐和近惯性流动在调节流动和混合中的作用以及输送的时间变异性。更好地了解其中的每一个，对于我们理解太平洋的大尺度环流，以及我们对深水航道流动的一般理解都是至关重要的。该项目需要一个协调的观测和建模方案，以测量和了解流经萨摩亚航道的水流和混合，其中包括以下内容：1)两次巡航，每次包括一个25天的重点系泊阵列，配备剖面仪，以及一次船舶检验，使用较低的ADCP/CTD和微结构剖面仪，以分辨水流和混合在时间和空间上的分布。两次巡航将间隔18个月，以根据对第一次巡航的数据分析，在第二次巡航中实现较长的监测时间序列和更清晰的重点。2)与20年前一样，在邮轮之间的同一地点部署了为期18个月的监测系泊装置，以获得对通过通道的财产和运输的另一种直接估计。3)不同复杂性和真实性的模型层次，从用于内波和交换流动问题的2-D MIT GCM配置到区域3-D运行，以评估下游溢流演变、旋转效应和远程内波源的影响。总而言之，这些模型将为观测带来更大规模的背景，并允许测试假设和参数相关性。4)详细的多波束航道测深图：深海环流预计将在最长的时间尺度上影响海洋对气候变化和大气二氧化碳增加的反应，而萨摩亚航道显然是大多数大型海洋模型中的一个弱点。这项工作直接解决了这些模型将需要模拟的过程，以便提高它们的预测能力。此外，社区认识到有必要扩大对萨摩亚航道的监测，就像在大西洋正在进行的努力一样(W线，RAPID)，以便评估太平洋翻转环流的十年变化。建议的测量和建模旨在确定这种监测阵列的最有效配置。在邮轮巡航的同时，还计划了各种外展活动，包括纪录片拍摄和在当地科学中心展出。该项目将在美国培养一名博士后和研究生，以及四名暑期本科生。此外，将加拿大和澳大利亚的科学家和学生纳入这项工作将支持国际合作。

Intellectual Merit:The bulk of Antarctic Bottom Water flowing northward into the abyssal North Pacific goes through the Samoan Passage, making it a key choke point in the overturning circulation of the Pacific. Detailed current meter and hydrographic observations confirm a strong northward flow of 6.0 Sverdrups. In addition, measurements are suggestive of extremely strong mixing and hydraulic control. However, many important questions remain unanswered, including the degree of hydraulic control of the flow, the strength of the mixing and the processes leading to it, the role of tidal and near-inertial flows in modulating the flow and the mixing, and the temporal variability of the transport. A better understanding of each of these is vital to our understanding of the large-scale circulation in the Pacific, as well as to our general understanding of flow through deep passages. This project entails a coordinated observational and modeling program to measure and understand flow and mixing through the Samoan Passage, which includes the following elements: 1) Two cruises, each including a 25-day focused mooring array with profiling instrumentation and a ship survey with lowered ADCP/CTD and microstructure profilers to resolve the currents and mixing in time and space. The cruises will be separated by 18 months to enable a long monitoring time-series and a sharper focus in the second cruise based on the analysis of data from the first. 2) An 18-month monitoring mooring array deployed between the cruises at the same location as that done 20 years prior in order to obtain another direct estimate of the properties and transport through the passage. 3) A hierarchy of models of differing complexity and realism, ranging from a 2-D MIT gcm configuration used for internal wave and exchange flow problems through regional 3-D runs to evaluate downstream overflow evolution, rotational effects and the influence of remote internal wave sources. Together, the models will bring a larger-scale context to the observations and allow testing of hypotheses and parameter dependencies. 4) Detailed multi-beam bathymetric mapping of the passage.Broader Impacts:The abyssal circulation is expected to influence the ocean's response to climate change and atmospheric carbon dioxide increases on the longest timescales, and the Samoan Passage is clearly a weak point in most large scale ocean models. This work directly addresses the processes that these models will need to simulate in order to improve their predictive capability. In addition, the community recognizes a need for extended monitoring of the Samoan Passage, in like manner to ongoing efforts in the Atlantic (Line W, RAPID), in order to assess decadal changes to the Pacific overturning circulation. The proposed measurements and modeling are intended to determine the most efficient configuration for such a monitoring array. A variety of outreach activities are planned in conjunction with the cruises, including documentary filming and exhibits at local science centers. The project will educate a postdoc and graduate student in the US, as well as 4 summer undergraduate fellows. In addition, the inclusion of Canadian and Australian scientists and students in the work will support international collaboration.