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

北冰洋是世界上唯一一个大西洋温暖、咸的沃茨与太平洋寒冷、新鲜的沃茨交汇的地方。因为太平洋水更新鲜，它更轻，漂浮在大西洋水（AW）之上，大西洋水温暖但沉重，下沉以填充北冰洋的深处。因此，太平洋沃茨就像一个物理屏障，阻止温暖的大西洋沃茨到达海面，在那里它们会导致海冰融化。由于大西洋水的流量大约是太平洋水流量的10倍，因此它具有影响海冰覆盖范围的巨大潜力。然而，由于它是咸的和重的，大西洋沃茨不能到达海洋表面，除非它们被积极地吸引到表面。海洋的潮汐和风为提升这些沉重的沃茨提供了能量来源，而将这些沃茨提升到水面的机制还没有得到很好的理解。该项目研究了麦肯齐峡谷-一个海底峡谷-如何作为一个管道，将温暖的大西洋深水引到浅水架，并将其混合成可能影响海冰过程的浅水近地表水体。湍流混合引起的热量再分配在控制北极海洋气候方面起着重要作用。这是一个独特的机会，记录了冰盖和北冰洋结构迅速演变期间的动态和机制。在这个项目中，研究小组使用了特殊的定制混合传感器和商业上可用的声学仪器，在已经计划好的现场实验中，允许表征热量通过湍流混合过程被吸引到北冰洋表面的速率。负责这种热传递的各个过程和能源（例如，潮汐、风和平均流）的变化取决于强迫联合收割机的细节如何组合，通常会产生控制净湍流热通量的混合地理热点。大陆斜坡已被确定为这样一种热量通道。该项目确定了与较平滑的博福特大陆坡相比，由于麦肯齐峡谷的斜坡切割地形的存在，温暖的大西洋水（AW）被修改和上涌的程度和机制。目标包括提供添加到北极观测网络（AON）电导率、温度和深度（CTD）调查部分的湍流仪器，以估计峡谷内和整个AON水文横断面的湍流消散率和热通量。博福特海，那里已知的湍流观测相对较少。作为这项工作的结果，该项目获得了一个全面的地图的湍流热通量和耗散率的博福特斜坡通过AON横断面和麦肯齐峡谷内。这项工作对于测量海洋动力学非常重要，并增加了对切割地形对北冰洋大西洋水向上热通量影响的理解。虽然峡谷只占北极海岸线的一小部分，但该项目的测量量化了它们对博福特海热量变化和传输的贡献。在更大的范围内，这项工作有助于改进在北极地区使用两种不同的CTD安装仪器计算湍流量的方法，该地区富含温暖的侧向侵入物，并且在多变和复杂地形的区域之间具有显著的热通量。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而被认为值得支持。

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.