Subpolar-Subtropical Connectivity of the North Atlantic Circulation

北大西洋环流的副极地-副热带连通性

• 批准号: 1537136
• 负责人: Xiaobiao Xu
• 金额: $ 45.12万
• 依托单位: Florida State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-15 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1537136&HistoricalAwards=false
• 关键词: Subpolar; Subtropical; Connectivity; North; Atlantic

The ocean, through its large capacity to store heat, plays a critical role in Earth's climate and climate variability. Warming of the world's oceans since 1955 accounts for approximately 93% of the warming of the Earth system. However, this warming is neither spatially uniform nor temporally constant. Superimposed on the global long-term trend is climate variability on inter-annual to inter-decadal time scales and regional to basin scales. Satellite altimeters and hydrographic observations show that the North Atlantic, including the sub-polar region, has rapidly become warmer and saltier since the early 1990s. An emerging picture is that the most recent 20 years or so of warming in the North Atlantic represents, in part, a transition of the Atlantic multi-decadal variability pattern from a cold to a warm phase. These decadal climate transitions involve changes both laterally in the sub-tropical and sub-polar gyres of the North Atlantic and vertically in the Atlantic Meridional Overturning Circulation (AMOC), a key component of the global heat and freshwater circulation system. This study of the North Atlantic circulation concentrates on a transition region around the Grand Banks of Newfoundland, where the effects of boundary currents and jets, recirculations, and mesoscale eddies (length scales typically less than 100 km) are dominant. Strong interactions occur in this transition region, laterally between the subpolar and subtropical gyres and vertically between the cold and warm limbs of the Atlantic Meridional Circulation (AMOC). There is evidence that this relatively compact region plays a key role in altering and even modulating the AMOC over a much larger scale and thus is important for the long-term, decadal variability of the Atlantic Ocean. Yet, despite many observational field programs, the dynamics and impacts of this region are not well understood. The project will contribute to understanding the variability of the AMOC by addressing the connectivity of the sub-polar and the sub-tropical gyres. The results of this model-data synthesis will be of particular significance to coupled climate models, which are central to understanding and predicting global climate change. The educational/outreach components of this project will be focused on cultivating scientific literacy with regards to ocean climate research in K-12 schools, at the university level, and in the local community through a variety of online resources/interactive tools for educators, the Florida State University Young Scholars program for high school students, and the "Scientists in the Schools" program. Finally, the requested funding will support a junior faculty member and a graduate student who will be trained in ocean modeling, data analysis and interpretation.Through ongoing major observation programs in the sub-polar and sub-tropical North Atlantic Ocean, oceanographers are making great strides toward a better understanding of the structure and variability of the AMOC within these sub-basins. The work proposed here complements these observations by focusing on key questions pertaining to what controls the circulation in between and how much the sub-polar to sub-tropical connectivity modulates the larger scale AMOC. This project aims to elucidate the physical dynamics that controls circulation in the transition region, especially the relative importance of the eddies and the deep western boundary current, and document the role and impact of the transition region on the larger scale circulation, especially the variability of the AMOC and water properties in the sub-polar and sub-tropical North Atlantic from inter-annual to decadal and longer time scales. The interaction of eddies and time mean circulations represents one of the greatest challenges to prediction of global climate variability, and it can be studied with the fine-grid resolution model included in this project. These objectives will be met by performing a detailed model-data synthesis study, combining numerical results from a suite of high-resolution Atlantic simulations using the HYbrid Coordinate Ocean Model (HYCOM) and existing observations (satellite altimetry, drifters/floats, hydrography, tracers, and mooring arrays). The three-dimensional Atlantic circulation will be quantified by performing analysis of water mass transport and transformation, passive tracers, and potential vorticity and momentum fluxes. It has been demonstrated that the eddy-resolving HYCOM represents the basic circulation features in the transition region and larger scale North Atlantic Ocean, including both time mean structure and temporal variability.

海洋通过其大量储存热量的能力在地球气候变化和气候变化中起着至关重要的作用。自1955年以来，世界海洋的变暖约占地球系统变暖的93％。但是，这种变暖既不是空间均匀的，也不是时间恒定。叠加在全球长期趋势上是青年到十年间时间尺度和盆地量表的气候变化。卫星高度计和水文观测表明，自1990年代初以来，北大西洋（包括亚极性区域）迅速变得更加温暖和咸。新兴的情况是，最近20年左右在北大西洋上变暖，部分代表了大西洋多年多年变化模式从寒冷到温暖阶段的过渡。这些十年气候转变涉及北大西洋亚热带和亚极点的横向变化，以及在大西洋子午倾斜循环（AMOC）中垂直变化，这是全球热和淡水循环系统的关键组成部分。这项对北大西洋循环的研究集中在纽芬兰大银行周围的过渡区域上，在那里边界电流和喷气机，再循环和中尺度涡流的影响（长度尺度通常小于100 km）是主导的。强烈的相互作用发生在该过渡区域，横向之间，在亚热带和亚热带之间，并在大西洋子午循环（AMOC）的寒冷和温暖的肢体之间进行垂直。有证据表明，这个相对紧凑的区域在更大规模的改变甚至调节AMOC方面起着关键作用，因此对于大西洋的长期，十年的变化很重要。然而，尽管有许多观察性现场计划，但该地区的动态和影响尚未得到充分理解。该项目将通过解决亚波尔和亚热带陀螺的连通性来理解AMOC的可变性。该模型数据合成的结果将对耦合的气候模型特别重要，这对于理解和预测全球气候变化至关重要。该项目的教育/宣传组成部分将集中在培养K-12学校，大学级别以及当地社区的海洋气候研究方面的科学素养，这是通过各种在线资源/互动工具为教育工作者，佛罗里达州立大学的年轻学者计划的高中生和“学校的科学家”计划。最后，要求的资金将支持初级教职员工和一名研究生，他们将接受海洋建模，数据分析和解释的培训。通过次极性和亚热带北大西洋的持续不断的主要观察计划，海洋学家正在对这些亚基蛋白内AMOC的结构和变异性更好地理解。此处提出的工作通过关注控制循环以及亚热带连接的多少关键问题来补充这些观察结果。该项目旨在阐明控制过渡区域循环的物理动力学，尤其是涡流和深层边界电流的相对重要性，并记录过渡区域对大规模循环的作用和影响，尤其是AMOC和水性在北大西洋学中从北大西洋中的变异性，尤其是从北大西洋学到前期和更长的时间尺度。涡流和时间平均循环的相互作用代表了预测全球气候变异性的最大挑战之一，并且可以通过本项目中包含的细网格分辨率模型进行研究。这些目标将通过进行详细的模型数据合成研究来实现，并结合了使用混合坐标海洋模型（HYCOM）和现有观测值（卫星高度计，drifters/floats/floats，水文，示踪剂和摩托车阵列）的高分辨率大西洋模拟的数值结果。三维大西洋循环将通过对水质量传输和转化，被动示踪剂以及潜在的涡度和动量通量进行分析来量化。已经证明，涡流分辨Hycom代表了过渡区域和较大规模的北大西洋的基本循环特征，包括时间平均结构和时间变化。