Offshore Export of Glacial Water and Ice in an Eddying Ocean

气候学中一个流行的假设是，大陆冰川和冰盖（“冰川水”）向北大西洋排放的大量水可能会扰乱海洋环流，导致气候变化。这一假说暗示，冰川水将作为一个有浮力的（轻的）表层从海岸向外扩散，并降低高纬度开阔海洋表面沃茨的密度。反过来，深层密集沃茨的形成和随之而来的向北的热量通量将减少。在这一项目中，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，研究冰川水排入北美东部沿着不同海洋区域的路径。该模型将模拟小规模涡流，并将与冰山模型相结合，以便测试各种海洋过程将融水和冰山向海洋迁移的能力。该项目将通过阐明各种海洋现象对液态和固态冰川水离岸输出的贡献，促进科学进步。它将通过以下方式对科学界有利：（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尺度涡旋，㈡限制对海底和沉积物岩心观察结果的解释，因为这些观察结果表明，深海-龙骨状的冰山沿着北大西洋西部边缘向南移动，冰川融水在过去30年里反复侵入大陆架，000年，和（iii）通过开放访问的网站共享实验结果。该项目将通过聘请一名研究生和三名本科生来支持教育。研究生将接触到现代海洋环流模型的能力，以研究气候相关的动力现象。三名本科生将利用旋转转盘进行淡水排放的实验室实验，并将实验的视频片段在线提供。将编写一份操作手册并与镜头链接，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造成气候变化的可能性;（ii）作为今后关于冰山对高纬度沃茨近海航运活动和石油/天然气勘探影响的模型研究的模板。将开发一个具有次中尺度分辨率的海洋环流-冰山耦合模型，并用于详细模拟冰川水以液态和固态形式沿沿着北美东部进入海洋的演变。该项目的具体目标是：㈠测试不同动力学现象在北美最后一次冰期（去冰期）的劳伦泰德冰盖冰川水离岸输出中的作用，㈡制定冰川水输出的参数化方法，用于粗分辨率气候模型，以及（iii）从LIS冰川水排放的角度对北美东部边缘的海底观测和沉积物记录的解释产生限制。为了实现这些目标，将在区域领域应用一个更大规模或更高分辨率的模型。该项目的工作计划包括三项任务。(1)海洋环流的数值模型将被配置为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)环流模式将与冰山模式相结合。(3)将用耦合模型进行试验，以阐明三个过程在冰川水向海输出中的作用：大浅滩附近的沿岸流分离，中大西洋湾的陆架断裂漩涡的运输，该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的评估来支持。影响审查标准。

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.