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.

气候学中普遍的假设认为，从大陆冰川和冰盖（“冰川水”）中排出大量水可能会破坏海洋循环并导致气候变化。在这一假设中隐含的是，冰川水将以浮力（轻度）的表面层从海岸扩散，并降低高纬度海洋中地表水的密度。反过来，将减少深茂密的水域和随之而来的北部热量。在这个项目中，将使用前所未有的空间分辨率的海洋循环系统模型来研究冰川水排出北美东部沿北美东部不同海洋地区的途径。该模型将模拟小规模的涡流，并将与冰山模型耦合，以便可以测试各种海洋过程运输融化和冰山海的能力。该项目将通过阐明各种海洋现象对液体和固体形式的冰川水的近海出口的贡献来促进科学的进步。通过（i）告知冰川水扰动实验的设计，这将是有利可图的观察结果表明，深冰冰山沿着北大西洋西部的边缘向南移动，并且在过去的30，000年中，冰川融化的冰川经常侵入大陆架以外，（iii）通过开放式网站分享实验结果。该项目将通过吸引研究生和三名本科生来支持教育。研究生将暴露于现代海洋循环模型研究气候相关性的动态现象的能力。三名本科生将通过旋转转盘进行淡水排放的实验室实验，并在线提供实验的录像。将写一份操作手册并链接到素材，因此科学家，老师和学生可以重复实验。最后，该项目将通过（i）更好地评估过去和未来冰川水的潜力以引起气候变化的潜力，以及（ii）作为对冰山对近海影响的未来模型研究的模板研究的模板在该项目的整个过程中，将开发并使用高纬度水域的运输活动和油/天然气勘探。在该项目的整个过程中，将开发并使用带有子尺度分辨率的耦合海洋循环 - 结冰模型以液体和固体形式进入北美东部的海洋。该项目的具体目标是（i）测试不同动力学现象在laurentide冰盖（LIS）近海出口中的作用，后者占据了北美的最后（de）冰川时期，（ii）至开发用于在粗分辨率气候模型中使用的冰川水出口的参数化，以及（iii）在解释海底观测值和从LIS的冰川水排放方面对海底观测和沉积物记录产生约束。为了实现这些目标，将在区域域中应用具有公里尺度或更高分辨率的模型。该项目的工作计划包括三个任务。 （1）将配置出海洋循环的数值模型，以代表北大西洋西部的两个海洋地区：纽芬兰的大银行和中大西洋的野事，包括哈特拉斯角附近的海洋地区。 （2）循环模型将耦合到冰山模型。 （3）将进行耦合模型的实验，以阐明三个过程在冰川水的海出出口中的作用：大岸边附近的沿海电流分离，在大西洋中部的货架上涡流运输，并在大西洋中部的涡流中运输，并与墨西哥湾流一起夹带该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子优点和更广泛的影响标准通过评估来支持的。