Collaborative Research: Mechanisms of Freshwater Exchange Across the East Greenland Shelf

从北极流出的淡水和格陵兰岛的冰融化有可能调节甚至关闭北大西洋亚极地的深层对流。控制这种交换的过程，以及它们如何依赖于外部因素，如风和北极的外流，在盆地尺度和气候模型中还不为人所知，也没有很好地解决。更好地了解大陆架上的淡水预算，以及这些水如何进入深海内部，对于改善气候模型和了解海洋如何应对气候变化至关重要。该项目计划使用数值海洋环流模型的层次结构进行基于动态的诊断，也将为其他敏感地区（如拉布拉多东海岸）的机制、位置和交换时间提供信息。该项目的研究结果将用于本科和研究生课程。由伍兹霍尔海洋学研究所暑期学生奖学金项目支持的本科生将在研究生的帮助下获得研究经验。该项目的材料也将用于海洋环流教科书。研究生将在约翰霍普金斯大学接受物理海洋学、地球物理流体动力学和海洋建模方面的培训。东格陵兰陆架与亚极地北大西洋和北欧海内部之间的淡水交换是大西洋经向翻转环流（AMOC）的维持和变率及其对大气强迫和北冰洋淡水流出变化的敏感性的关键因素。一个现实的、非常高分辨率的东格陵兰陆架和邻近深海的区域模型将与理想化的、面向过程的模型和现场观测相结合，以确定这种交流的强度、机制和敏感性。可能对这种跨大陆架交换很重要的过程包括：表面和底部埃克曼层；非线性涡流通量；局地和远地风强迫；以及风力驱动的海冰。我们将在一系列现实的模型运行中对这种交换进行诊断。实验将按照理想模型进行设计，隔离相关过程，以便进一步研究和理解，并将与现场系泊和水文观测以及遥感海冰数据进行比较。该项目的主要目标是基本了解是什么控制着淡水从陆架流向盆地内部，以及它是如何依赖于外部强迫（风、北极流出、格陵兰径流）和环境条件（如海底测深和环境分层）的。

Freshwater flowing out of the Arctic and from Greenland ice melt has the potential to modulate or even shut down deep convection in the sub-polar North Atlantic. The processes that control this exchange, and how they depend on external factors such as wind and outflow from the Arctic, are not well known and are not well resolved in basin-scale and climate models. Better understanding of the freshwater budget on the shelf, and how these waters get into the deep ocean interior, is essential to improve climate models and understand how the ocean will respond to a changing climate. The dynamically-based diagnostics planned in this project using a hierarchy of numerical ocean circulation models will also inform on mechanisms, locations, and times of exchange in other sensitive areas, such as the east coast of Labrador. Findings from the project will be used in undergraduate and graduate classes. Undergraduate students supported by the Woods Hole Oceanographic Institution Summer Student Fellowship program and assisted by graduate students will gain research experience. Material from the project will also be used in a textbook on ocean circulation. A graduate student will be trained in physical oceanography, geophysical fluid dynamics, and ocean modeling at Johns Hopkins University. The exchange of freshwater between the east Greenland shelf and the interior of the sub-polar North Atlantic and Nordic Seas is a key element in the maintenance and variability of the Atlantic Meridional Overturning Circulation (AMOC) and its sensitivity to changes in atmospheric forcing and freshwater outflow from the Arctic Ocean. A realistic, very high resolution, regional model of the east Greenland shelf and adjacent deep ocean will be combined with idealized, process oriented models and in-situ observations to identify the strength, mechanisms, and sensitivity of this exchange. Processes likely important for this cross-shelf exchange include: surface and bottom Ekman layers; nonlinear eddy fluxes; local and remote wind-forcing; and wind-driven sea ice. The exchange will be diagnosed in a series of realistic model runs. Experiments will be designed with the idealized model to isolate the relevant processes for further study and understanding, and comparisons will be made with in-situ mooring and hydrographic observations and remotely sensed sea ice data. The main goal of the project is to reach a basic understanding of what controls the flux of freshwater from the shelf to the basin interior and how it depends on external forcing (wind, outflow from the Arctic, Greenland runoff) and environmental conditions such as bottom bathymetry and the ambient stratification.