RAPID: Quantifying turbulent mixing and heat flux in the Mackenzie Canyon and across the Beaufort continental slope in the Arctic Ocean

RAPID：量化麦肯齐峡谷和北冰洋波弗特大陆坡的湍流混合和热通量

• 批准号: 2042692
• 负责人: Amy Waterhouse
• 金额: $ 7.13万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-08-15 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2042692&HistoricalAwards=false
• 关键词: RAPID; Quantifying; turbulent; mixing; heat; RAPID; Quantifying; turbulent; mixing; heat

The Arctic Ocean is the one place in the world where the warm, salty waters from the Atlantic Ocean meet the colder and fresher waters of the Pacific Ocean. Because the Pacific Water is fresher, it is lighter and floats above Atlantic Water (AW), which is warm but heavy and sinks to fill the depths of the Arctic Ocean. As such, the Pacific waters act as a physical barrier that prevents warm Atlantic waters from reaching the surface where they can cause increased melting of sea ice. Because the flow of Atlantic Water is approximately ten times stronger than the flow of Pacific Water, it represents a huge potential for influencing sea ice coverage. However, because it is salty and heavy, Atlantic waters cannot reach the ocean surface unless they are actively drawn to the surface. The ocean’s tides and winds provide energy sources for lifting these heavy waters and the mechanisms for raising these waters to the surface are not well understood. This project studies how the Mackenzie Canyon - a submarine canyon - can act as a conduit to draw up the deep, warm Atlantic Water to the shallow shelves, and mix it into shallow, near-surface water masses where it may influence sea-ice processes. Redistribution of heat by turbulent mixing plays an important role in controlling the ocean climate in the Arctic. This is a unique opportunity that documents the dynamics and mechanisms during a time where ice-cover and the Arctic Ocean structure is rapidly evolving. For this project, the research team uses special custom-made mixing sensors and a commercially available acoustic instrumentation aboard an already-planned field experiment to allow characterization of the rate at which heat is being drawn to the Arctic Ocean’s surface through turbulent mixing processes. The individual processes and sources of energy responsible for this heat transfer (e.g., tides, winds, and mean flow) vary depending on how details of the forcing combine, often creating geographic hotspots of mixing that dominate the net turbulent heat fluxes. Continental slopes have been identified as one such conduit for heat. This project determines how much and by what mechanism warmer Atlantic Water (AW) is modified and upwelled due to the presence of the slope-incising topography of the Mackenzie Canyon, compared to the smoother Beaufort continental slope. Aims include providing turbulent instrumentation added to the Arctic Observing Network (AON) conductivity, temperature, and depth (CTD) survey sections to estimate turbulent dissipation rate and heat fluxes within the canyon and across the AON hydrographic transects of the Beaufort Sea, where there are relatively few known turbulence observations. As a result of this work, the project obtains a comprehensive map of the turbulent heat flux and dissipation rate across the Beaufort slope via the AON transects and within the Mackenzie Canyon. This work is important for measuring ocean dynamics and increases understanding of the influence of incising topography to the upward heat flux from the Atlantic Water in the Arctic Ocean. While canyons represent a small percentage of the coastline in the Arctic, this project’s measurements quantify their contribution to the modification and transport of heat in the Beaufort Sea. On a larger scale, this work contributes to refining methods for calculating turbulent quantities using two different CTD-mounted instruments in the Arctic, a region rich with warm lateral intrusions and significant heat flux across regions of variable and complex topography.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.

北极海是世界上一个地方的一个地方，来自大西洋的温暖，咸水会遇到太平洋的寒冷和新鲜水域。由于太平洋水更新鲜，所以它更轻，漂浮在大西洋水（AW）上方，该水温暖但沉重，下沉以填补北极海的深度。因此，太平洋水域充当物理障碍，可防止温暖的大西洋水域到达可以引起海冰融化增加的表面。由于大西洋水的流量比太平洋水的流量强约十倍，因此它代表了受影响的海冰覆盖范围的巨大潜力。但是，由于它咸而沉重，大西洋水域无法到达海洋表面，除非它们被积极地吸引到表面。海洋的潮汐和风提供了抬高这些大水域的能源，将这些水升至地面的机制不太理解。该项目研究了麦肯齐峡谷（Mackenzie Canyon）如何充当渠道，将深层，温暖的大西洋水从浅层架上绘制，并将其混合到可能影响海上冰过程的浅层水质中。通过湍流混合对热量的重新分布在控制北极的海洋气候方面起着重要作用。这是一个独特的机会，可以在冰覆盖和北极海洋结构迅速发展的时期记录动态和机制。对于该项目，研究团队使用特殊的定制混合传感器和已计划的现场实验上的市售声学仪器，以通过湍流混合过程来表征将热量吸引到北极海洋表面的速率。负责这种传热的单个过程和能源（例如潮汐，风和平均流）取决于强迫的细节结合在一起，通常会产生占主导地位的净湍流热通量的混合地理热点。大陆槽已被确定为热量的管道。与光滑的Beaufort大陆插槽相比，该项目确定了多少机制和通过哪种机理变暖的大西洋水（AW）进行了修改和上升，这是由于Mackenzie Canyon的斜率构成地形而被修改和上升的。目的包括提供在北极观测网络（AON）电导率，温度和深度（CTD）调查部分中添加的湍流仪器，以估计峡谷内以及Beaufort Sea的AON水文样道内的湍流耗散率和热通量，在相对较少的已知湍流观察中。由于这项工作，该项目通过Aon crants和Mackenzie Canyon内部获得了湍流的热通量和耗散率的综合图。这项工作对于衡量海洋动力学和增加对北极海洋大西洋水对向上热通量的影响的理解非常重要。虽然峡谷代表北极的一小部分海岸线，但该项目的测量值量化了其对Beaufort Sea热量改造和运输的贡献。 On a larger scale, this work contributes to refining methods for Calculating turbulent quantities using two different CTD-mounted instruments in the Arctic, a region rich with warm lateral intrusions and significant heat flux across regions of variable and complex topography.This award reflects NSF's statutory mission and has been deemed precious of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.