Offshore Export of Glacial Water and Ice in an Eddying Ocean

涡流海洋中冰川水和冰的近海输出

• 批准号: 1903427
• 负责人: Olivier Marchal
• 金额: $ 79.99万
• 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: 2019
• 资助国家: 美国
• 起止时间: 2019-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1903427&HistoricalAwards=false
• 关键词: Offshore; Export; Glacial; Water; Ice

A popular hypothesis in climatology posits that the discharge of large amounts of water from continental glaciers and ice sheets ("glacial water") into the North Atlantic may disrupt ocean circulation and cause climate change. Implicit in this hypothesis is that the glacial water would spread away from the coast, as a buoyant (light) surface layer, and decrease the density of surface waters in the open ocean at high latitudes. In turn, the formation of deep dense waters and the attendant northward flux of heat would be reduced. In this project, a computer model of ocean circulation, with unprecedented spatial resolution, will be used to study the pathways of glacial water discharged into different oceanic regions along eastern North America. The model will simulate small-scale eddies and will be coupled to an iceberg model, so that the ability of various oceanic processes to transport meltwater and icebergs seaward could be tested. This project will promote the progress of science by elucidating the contribution of various oceanic phenomena to the offshore export of glacial water in both liquid and solid forms. It will be profitable to the scientific community by (i) informing the design of glacial water perturbation experiments performed with coarse-resolution climate models which cannot explicitly represent small-scale eddies in the ocean, (ii) constraining the interpretation of seafloor and sediment core observations which suggest that deep-keeled icebergs moved southward along the western North Atlantic margin and that glacial meltwater intruded recurrently beyond the continental shelf during the last 30,000 years, and (iii) sharing experimental results via open-access web sites. This project will support education by engaging a Graduate Student and three Undergraduate Students. The Graduate Student will be exposed to the capability of modern ocean circulation models to study dynamical phenomena of climatic relevance. The three Undergraduate Students will conduct laboratory experiments of freshwater discharge with rotating turntables and make the video footage of the experiments available on-line. A how-to manual will be written and linked to the footage, so scientists, teachers, and students could repeat the experiments. Finally, this project will benefit society by (i) providing a better assessment of the potential of both past and future glacial water discharges to cause climate change, and (ii) serving as a template for future model studies on the impact of icebergs on offshore shipping activities and oil/gas exploration in high-latitude waters.In more technical terms, over the course of this project, a coupled ocean circulation-iceberg model with submesoscale resolution will be developed and used to produce detailed simulations of the evolution of glacial water entering the ocean along eastern North America in liquid and solid forms. The specific objectives of this project are (i) to test the role of different dynamical phenomena in the offshore export of glacial water from the Laurentide Ice Sheet (LIS), which occupied North America the last (de)glacial periods, (ii) to develop a parameterization of glacial water export for use in coarse-resolution climate models, and (iii) to yield constraints on the interpretation of seafloor observations and sediment records from the eastern North American margin in terms of glacial water discharges from the LIS. To meet these objectives, a model with kilometer-scale or higher resolution will be applied in regional domains. The work plan of this project includes three tasks. (1) A numerical model of ocean circulation will be configured to represent two oceanic regions in the western North Atlantic: the Grand Banks of Newfoundland, and the Middle Atlantic Bight including the oceanic region near Cape Hatteras. (2) The circulation model will be coupled to an iceberg model. (3) Experiments with the coupled model will be conducted to elucidate the roles of three processes in the seaward export of glacial water: coastal current separation near the Grand Banks, transport by shelfbreak eddies in the Middle Atlantic Bight, and entrainment with the Gulf Stream near Cape Hatteras.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.

气候学中的一个流行假设认为，大陆冰川和冰盖（“冰川水”）中的大量水排放到北大西洋可能会扰乱海洋环流并导致气候变化。这一假设隐含的含义是，冰川水会作为浮力（轻）表层从海岸扩散开来，并降低高纬度开放海洋中表层水的密度。反过来，深层稠密水域的形成以及随之而来的向北的热量通量将会减少。在该项目中，将使用具有前所未有的空间分辨率的海洋环流计算机模型来研究冰川水排入北美东部不同海洋区域的路径。该模型将模拟小规模涡流，并将与冰山模型耦合，以便测试各种海洋过程将融水和冰山输送到海洋的能力。该项目将通过阐明各种海洋现象对液态和固态冰川水向近海输出的贡献来促进科学进步。通过以下方式，它将对科学界有利：（i）为使用粗分辨率气候模型进行的冰川水扰动实验的设计提供信息，这些模型无法明确代表海洋中的小规模涡流；（ii）限制对海底和沉积物核心观测的解释，这些观测表明深龙骨冰山沿着北大西洋西部边缘向南移动，冰川融水反复侵入到更远的地方。 过去 30,000 年的大陆架，以及 (iii) 通过开放访问网站分享实验结果。该项目将通过一名研究生和三名本科生来支持教育。研究生将接触现代海洋环流模型的能力，以研究与气候相关的动态现象。这三名本科生将利用旋转转盘进行淡水排放实验室实验，并将实验视频上传到网上。将编写一份操作手册并将其链接到视频中，以便科学家、教师和学生可以重复实验。最后，该项目将通过以下方式造福社会：（i）更好地评估过去和未来冰川水排放导致气候变化的潜力，以及（ii）作为未来冰山对近海航运活动和高纬度水域石油/天然气勘探影响的模型研究的模板。用更专业的术语来说，在该项目的过程中，将开发一个具有亚中尺度分辨率的海洋环流-冰山耦合模型并用于产生 详细模拟冰川水以液体和固体形式沿着北美东部进入海洋的演变。该项目的具体目标是（i）测试不同动力现象在劳伦泰冰盖（LIS）近海出口冰川水中的作用，该冰盖在最后（消）冰期占据北美，（ii）开发用于粗分辨率气候模型的冰川水出口参数化，以及（iii）对来自海底观测和沉积物记录的解释产生限制。 就 LIS 冰川水排放量而言，北美东部边缘。为了实现这些目标，公里级或更高分辨率的模型将应用于区域领域。本项目工作计划包括三项任务。 (1) 将配置海洋环流数值模型来代表北大西洋西部的两个海洋区域：纽芬兰大浅滩和中大西洋湾，包括哈特拉斯角附近的海洋区域。 (2) 环流模型将与冰山模型耦合。 (3) 将进行耦合模型实验，以阐明冰川水向海输出的三个过程的作用：大浅滩附近的沿岸流分离、中大西洋湾的断架涡流的输送以及哈特拉斯角附近的湾流夹带。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力评估进行评估，认为值得支持。 优点和更广泛的影响审查标准。