A Process Study of the Atlantic Water Transport over the Greenland-Scotland Ridge

格陵兰-苏格兰海岭大西洋水运过程研究

• 批准号: 1634886
• 负责人: Jiayan Yang
• 金额: $ 47.02万
• 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: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1634886&HistoricalAwards=false
• 关键词: Process; Study; Atlantic; Water; Transport

The Greenland-Scotland Ridge (GSR) system plays an outsized role in the climate system. In the surface layer, the warm and saline Atlantic Water flows northward across the GSR and the light Polar Waters moves southward mainly through the Denmark Strait. In the lower layer, the overflow transports the cold and dense water over the GSR into the Atlantic Ocean. This inflow of Atlantic Water is the primary oceanic heat transport to the Arctic Ocean and the Nordic Seas. Changes in this transport over the GSR affect the state of the ocean, climate, sea ice and ecosystem in the Nordic Seas and the Arctic Ocean. Yet there is still a significant gap in understanding how the transport of the Atlantic Water is responding to changes in atmospheric forcing. The mean transport of the Atlantic Water inflow is primarily forced by buoyancy flux. Variability on seasonal to inter-annual time scales are attributable to both wind stress and buoyancy fluxes, but there remain many uncertainties regarding how and from where the atmospheric forcing influences the Atlantic Water transport. The Atlantic Water inflow is influenced not only by atmospheric forcing locally at the GSR, but in the two basins that it is connected with. It also interacts with the Nordic Seas Overflow. The proposed study seeks to identify essential mechanisms and processes that link changes in the atmosphere to Atlantic Water transport. It will help assessments of climate prediction models and reduce uncertainties of a potential key driver for future changes in the Arctic climate system. This study will contribute to the Ocean Outlook initiative, a joint venture established in 2015 between WHOI and the Bergen Marine Research Cluster in Norway and will also further the goal of enhancing trans-Atlantic collaborations as outlined in the Galway agreement.The Greenland-Scotland Ridge (GSR) is the main topographic barrier between the Atlantic and the Nordic Seas/Arctic Ocean. It restricts flows between the warm and saline Atlantic Ocean and the cold and fresh Arctic Ocean. The exchange flow of Atlantic Water over the GSR is influenced by multiple and complex processes and forcing. This project will examine key dynamical processes that govern exchange flows between the Atlantic Ocean and the Nordic Seas that are separated by a shallow GSR. Process studies using numerical models with available observations and a data-assimilated ocean estimate will be conducted to examine how local and remote forcing gives rise to variations in Atlantic Water transport over the GSR. The goal is to develop a better understanding of key mechanisms and processes that govern the Atlantic Water inflow and its variability across the GSR. First a 2-layer model will be used to develop intuitions, and to examine leading order dynamical balances. The efficiency of the model allows multiple simulations over several decades. The simplicity and transparency in dynamics are ideally suited for developing ideas and elucidating competing mechanisms and in isolating key processes. The mechanisms and processes that are identified in the 2-layer model will be examined by using the more realistic 1/12 degree Hybrid Coordinate Model (HYCOM). The HYCOM model will also be used to examine the role of buoyancy forcing in the variability of Atlantic Water transport. The data-assimilated Estimating the Circulation & Climate of the Ocean version 4 (ECCO 4) and in situ and satellite observations will be used to check the model?s consistency with observational data and data-assimilated estimates. The premise is that the ECCO 4, with its assimilation of temperature/salinity profiles, satellite sea surface height and bottom pressure, represents the variability more realistically than ocean models without data assimilation. Overall, the study will improve current understanding of a key oceanic process that is very important for ocean circulation and climate in both Arctic and Atlantic. Exchange flows over topography between two basins are common features in the world?s ocean circulation system. Other examples include the flow from the Pacific to the Arctic Ocean through Bering Strait, throughflows in the Japan Sea, etc. This study will result in a better understanding of intrinsic dynamics that are important to general cases of cross-ridge flows between two basins in the world ocean.

格陵兰-苏格兰山脊(GSR)系统在气候系统中扮演着非常重要的角色。在表层，温暖和咸水的大西洋水向北穿过GSR，而轻的极地水主要通过丹麦海峡向南移动。在低层，溢流将GSR上的冷水和稠密水输送到大西洋。大西洋水的这种流入是北冰洋和北欧海洋的主要海洋热量输送。GSR上的这种输送的变化会影响北欧海和北冰洋的海洋、气候、海冰和生态系统的状况。然而，在理解大西洋水的输送如何应对大气强迫的变化方面仍有很大差距。大西洋水的平均输运主要是由浮力通量强迫的。季节到年际时间尺度上的变化既可归因于风应力，也可归因于浮力通量，但关于大气强迫如何影响大西洋水运以及从哪里影响大西洋水运仍存在许多不确定性。大西洋水的流入不仅受到GSR局地大气强迫的影响，而且在与之相连的两个盆地中也受到影响。它还与北欧泛滥的海洋相互作用。拟议的研究试图确定将大气变化与大西洋水运联系起来的基本机制和过程。它将有助于评估气候预测模型，并减少北极气候系统未来变化的潜在关键驱动因素的不确定性。这项研究将有助于海洋展望倡议，这是世界卫生组织和挪威卑尔根海洋研究集群于2015年建立的一个合资企业，还将促进戈尔韦协定中概述的加强跨大西洋合作的目标。格陵兰-苏格兰海脊是大西洋和北欧海/北冰洋之间的主要地形屏障。它限制了温暖而咸的大西洋和寒冷而新鲜的北冰洋之间的流动。大西洋水在GSR上的交换流动受多个复杂的过程和强迫的影响。该项目将研究控制大西洋和北欧之间交换流动的关键动力过程，这些流动被浅层GSR隔开。将利用现有观测的数值模式和数据同化的海洋估计进行过程研究，以审查本地和远程强迫如何引起GSR上大西洋水输送的变化。其目标是更好地了解管理大西洋水流入及其在GSR的可变性的关键机制和过程。首先，将使用一个两层模型来发展直觉，并检查前导顺序动态平衡。该模型的效率允许在几十年内进行多次模拟。动力学的简单性和透明性非常适合于开发想法、阐明相互竞争的机制以及隔离关键过程。在2层模型中确定的机制和过程将通过使用更真实的1/12度混合坐标模型(HYCOM)来检验。HYCOM模式还将被用来研究浮力强迫在大西洋水运可变性中的作用。利用海洋环流与气候同化估算第4版(ECCO4)资料、现场观测资料和卫星观测资料，检验S模式与观测资料和资料同化估算资料的一致性。前提是ECCO4通过同化温度/盐度廓线、卫星海面高度和海底气压，比没有数据同化的海洋模式更真实地反映了这种变化。总体而言，这项研究将改善目前对一个关键的海洋过程的理解，该过程对北极和大西洋的海洋环流和气候都非常重要。两个盆地之间的地形交换流动是世界上的共同特征--S海洋环流系统。其他例子包括通过白令海峡从太平洋流向北冰洋的水流、日本海的贯通水流等。这项研究将有助于更好地理解内在动力学，这些内在动力学对于世界大洋两个盆地之间的跨脊水流的一般情况很重要。

项目成果

Structure and Formation of Anticyclonic Eddies in the Iceland Basin

冰岛盆地反气旋涡的结构和形成

• DOI: 10.1029/2018jc013886
• 发表时间: 2018
• 期刊: Journal of Geophysical Research: Oceans
• 作者: Zhao, Jian;Bower, Amy;Yang, Jiayan;Lin, Xiaopei;Zhou, Chun
• 通讯作者: Zhou, Chun

How is New England Coastal Sea Level Related to the Atlantic Meridional Overturning Circulation at 26° N?

新英格兰沿海海平面与北纬 26° 的大西洋经向翻转环流有何关系？

• DOI: 10.1029/2019gl083073
• 发表时间: 2019
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Piecuch, Christopher G.;Dangendorf, Sönke;Gawarkiewicz, Glen G.;Little, Christopher M.;Ponte, Rui M.;Yang, Jiayan
• 通讯作者: Yang, Jiayan

A sea change in our view of overturning in the subpolar North Atlantic

• DOI: 10.1126/science.aau6592
• 发表时间: 2019-02-01
• 期刊: SCIENCE
• 影响因子: 56.9
• 作者: Lozier, M. S.;Li, F.;Zhao, J.
• 通讯作者: Zhao, J.