Canyons Influence on Cross-shelf Exchange - When Dense Water Goes Down, Warm Water Comes Up

峡谷对跨陆架交换的影响 - 当浓水下降时，温水上升

• 批准号: 2147884
• 负责人: Claudia Cenedese
• 金额: $ 108.36万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-03-01 至 2025-02-28
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2147884&HistoricalAwards=false
• 关键词: Canyons; Influence; Cross; shelf; Exchange

This project will examine the dynamics of the cross-shelf exchange in a slope canyon induced by dense shelf water descending into the canyon. The case to be examined in the Antarctica region is of global significance because the offshore flowing dense water forms Antarctic Bottom Water and thus affects the global meridional circulation, while the onshore heat transport induced by the return flow drives glacial ice melt and therefore contributes to sea level rise. These important processes will be investigated through a combined laboratory and numerical approach. The project will explore the leading order dynamics controlling the cross-shelf exchange of momentum, heat and tracers when dense water descends a canyon. Key locations to measure dense shelf water offshore transport and offshore water onshore transport will be identified to provide guidance to future field campaigns. This proposal will support the Ph.D. research of a graduate student, and other students will be involved through the PIs’ active lab-groups. The experimental work will utilize the Geophysical Fluid Dynamics Laboratory at WHOI. In Years 1 and 3, the Geophysical Fluid Dynamics Laboratory Open Week event will target undergraduate and graduate students, postdocs, K-12 students. This event will host 10 hands-on demonstrations and displays. Material from this project will be used in educational activities by the Co-PIs. Preliminary numerical modeling revealed two unexpected flows in the Antarctic coastal region. The first is a current on the continental shelf east of the canyon, which contributes to the cross-shelf exchange by transporting a third of dense water across the shelf-break upstream (from the perspective of the Kelvin wave propagation) of the canyon. The second is the onshore intrusion into the canyon of deep offshore water, some of which is able to reach the coast. The project will combine numerical modeling with laboratory tank experiments to test two hypotheses: first, that a substantial fraction of dense water generated on the shelf over the head of a canyon flows onto the upstream shelf and eventually moves offshore into the slope sea on the upstream side of the canyon; and second, dense water descending down a canyon induces an onshore return flow of deep offshore water in the canyon. It is also hypothesized that this onshore flow originates on the continental slope downstream of the canyon and exits the canyon onto the continental shelf upstream of the canyon. The Regional Ocean Modeling System (ROMS) will be used to simulate the formation and subsequent transport of Dense Shelf Water (DSW) generated in a coastal region, as well as the motion of ambient water, in an idealized continental shelf and slope system. Idealized laboratory experiments using a rotating glass tank with a very similar set up as the numerical simulations will be used. These experiments will test whether the assumptions and parameterizations used in the numerical model are influencing the dynamics of interest. In addition, agreement between the laboratory and numerical results will provide confidence that the relevant dynamics are correctly captured in the laboratory.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.

该项目将研究由稠密的陆架水下降到峡谷中引起的跨陆架交换的动态，在南极洲地区研究的案例具有全球意义，因为近海流动的稠密水形成了南极底水和水。从而影响全球经向环流，而回流引起的陆上热传输驱动冰川融化，从而导致海平面上升。该项目将通过实验室和数值方法相结合的方式来研究这些重要过程。当浓水从峡谷下降时控制跨大陆架交换的动量、热量和示踪剂的秩序动力学将被确定，以测量浓水陆上运输和近海水陆上运输的关键位置，为未来的实地活动提供指导。一名研究生和其他学生将通过 PI 的活跃实验室小组参与实验工作。第一年和第三年将利用 WHOI 的地球物理流体动力学实验室。动力学实验室开放周活动将针对本科生和研究生、博士后、K-12 学生。该活动将举办 10 场实践演示和展示，该项目的材料将用于初步数值建模的教育活动。揭示了南极沿海地区的两种意想不到的水流，第一种是峡谷以东的大陆架上的水流，它通过将三分之一的浓水输送到上游的陆架断裂处来促进跨大陆架交换。 （从开尔文波传播的角度）第二个是向近海深水峡谷的陆上侵入，其中一些能够到达海岸。有两个假设：第一，峡谷顶部陆架上产生的大部分浓水流到上游陆架上，最终向近海移动，进入峡谷上游侧的斜坡海；第二，浓水向下下降；一个峡谷引起了峡谷中近海深水的陆上回流。区域海洋模拟系统还发现，这种陆上水流起源于峡谷下游的大陆坡，并从峡谷流出到峡谷上游的大陆架。 ROMS）将用于模拟沿海地区产生的密集陆架水（DSW）的形成和随后的输送，以及理想化大陆架和斜坡中环境水的运动使用与数值模拟非常相似的旋转玻璃罐进行理想化实验室实验，这些实验将测试数值模型中使用的假设和参数化是否影响感兴趣的动力学。实验室和数值结果将为实验室正确捕获相关动态提供信心。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。