NSFGEO-NERC: Collaborative Research: Subpolar North Atlantic Processes - Dynamics and pRedictability of vAriability in Gyre and OverturNing (SNAP-DRAGON)

NSFGEO-NERC：合作研究：北大西洋次极过程 - 环流和翻转变化的动力学和可预测性 (SNAP-DRAGON)

• 批准号: 2038422
• 负责人: Patrick Heimbach
• 金额: $ 7.59万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2038422&HistoricalAwards=false
• 关键词: NSFGEO; NERC; Collaborative; Research; Subpolar

This is a project that is jointly funded by the National Science Foundation's Directorate of Geosciences (NSF/GEO) and the National Environment Research Council (NERC) of the United Kingdom (UK) via the NSF/GEO-NERC Lead Agency Agreement. This Agreement allows a single joint US/UK proposal to be submitted and peer-reviewed by the Agency whose investigator has the largest proportion of the budget. Upon successful joint determination of an award, each Agency funds the proportion of the budget and the investigators associated with their own country. The subpolar North Atlantic Ocean, stretching between the UK, Greenland, and Canada, plays a crucial role in local and global climate. This is the critical region where much of the warm water flowing northward in the upper North Atlantic releases its heat to the atmosphere and is converted to cold, dense water, before flowing southward again at depth in what is known as the Atlantic overturning circulation. The large amount of heat this circulation carries northward and releases to the atmosphere impacts the track of storms and determines the weather over western Europe. The overturning circulation also has profound implications for African rainfall and hurricane development via its effect on sea surface temperature at lower latitudes. In addition, the sinking of water in the subpolar region ventilates the deep ocean, transferring heat and carbon away from the surface and moderating the impact of anthropogenic greenhouse gases on surface temperature. Any warm water which does not sink in the subpolar region recirculates or carries its heat further north towards the Arctic, influencing sea-ice conditions and polar marine ecosystems before it too sinks and flows south. This study aims to produce a step change in our understanding of the processes that link atmospheric changes to subpolar ocean variability, their implications for ocean and climate predictability in this region, and the degree to which we can trust their representation in climate models. Recently, the first ever observations of the overturning circulation in the subpolar North Atlantic have been made by the Overturning in the Subpolar North Atlantic Program (OSNAP, www.o-snap.org). These have revealed large amplitude variations in the overturning and raised questions about the locations and processes that give rise to this variability and its likely impact on surface ocean conditions and climate. Representing this region properly in climate models is essential for making useful climate predictions on seasonal, interannual, decadal and longer timescales. However, the current generation of models struggle to represent the processes known to be important here and disagree with the observations on the locations in which warm water is transformed into dense water. The disagreements limit our confidence in model predictions. The scientific community cannot assess model performance properly because there is limited understanding of all the links between atmospheric conditions and ocean circulation variability. This project will combine OSNAP and other observations with numerical models that can represent small-scale processes to reveal the cause of the variations in subpolar ocean circulation. Once it is clear which processes are most important and how they work, the team will be able to establish what climate models are getting wrong and suggest improvements. This will improve predictions of ocean and climate variability in the subpolar North Atlantic and beyond. The team will investigate how cold, dense waters find their way into the boundary currents that export them to the south. It will establish the role that winds play, which is likely more complicated than we have assumed in the past and it will determine the impact on overturning variability of changes in freshwater export from the Arctic and Greenland. To characterize and quantify these key processes, in addition to using ocean observations, the investigators will perform "What if?" experiments in ocean models, asking questions such as: what happens to the subpolar ocean circulation if the atmospheric jet stream over the Atlantic shifts or strengthens? They will use statistical methods more common in weather forecasting to figure out how subpolar ocean properties and overturning connect to potentially predictable larger-scale atmospheric circulation patterns. Innovative ways of combining models with observations will be used to determine a best estimate of the evolution of the subpolar North Atlantic over the OSNAP observation period.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.

这是一个由国家科学基金会地球科学局（NSF/GEO）和英国国家环境研究委员会（NERC）共同资助的项目。该协议允许该机构提交和同行评审的一项联合提案，其调查员的预算比例最大。成功确定裁决后，每个机构为预算的比例和与自己国家相关的调查人员提供了资金。在英国，格陵兰岛和加拿大之间延伸的北大西洋北大西洋在地方和全球气候中起着至关重要的作用。这是北大西洋上部向北流动的许多温水将其热量释放到大气中，并转化为冷浓水，然后在深度再次向南流动，在所谓的大西洋翻转循环中再次向南流动。这种循环的大量热量向北延伸，并释放到大气上，影响了风暴的轨道，并决定了西欧的天气。倾覆的循环也对非洲降雨和飓风发展具有对较低纬度的海面温度的影响。另外，亚极区域的水沉没会通风深海，将热量和碳从表面转移，并节省人为温室气体对表面温度的影响。任何不下沉在亚极区域的温水都会循环或向北向北延伸或将热水朝向北极，影响海冰条件和极地海洋生态系统，然后它也会下沉并向南流动。这项研究旨在在我们对将大气变化与亚极海洋变异性联系在一起的过程中的理解，对海洋和该地区的气候可预测性以及我们可以在气候模型中信任其表示的程度的过程中产生步骤变化。最近，在北大西洋北部大西洋计划（OSNAP，www.o-snap.org）中倾覆，对北大西洋倾覆的循环的第一个观察结果是。这些揭示了有关倾覆的幅度变化很大，并提出了有关导致这种变异性及其对地表海洋条件和气候的可能影响的位置和过程的问题。在气候模型中适当地代表该区域对于对季节性，年际，年龄段和更长的时间标准进行有用的气候预测至关重要。但是，当前的模型很难代表这里已知的过程很重要，并且不同意温水转化为密集水的位置上的观察结果。分歧限制了我们对模型预测的信心。科学界无法正确评估模型性能，因为对大气条件与海洋循环变异性之间的所有联系的了解有限。该项目将将OSNAP和其他观察结果与数值模型相结合，这些模型可以代表小规模的过程，以揭示下极海洋循环的变化原因。一旦清楚哪些过程是最重要的以及它们的工作方式，团队将能够确定哪些气候模型出错并建议改进。这将改善对海洋和气候变异性的预测。该团队将调查茂密的水域如何进入将它们导出到南部的边界电流。它将确定风能发挥的作用，这可能比我们过去假设的要复杂得多，这将决定对北极和格陵兰岛淡水出口变化的颠覆变化的影响。为了表征和量化这些关键过程，除了使用海洋观测外，研究人员还将执行“如果？”海洋模型中的实验，询问以下问题：如果大西洋偏移或增强大气中的喷气流，下极海洋循环会发生什么？他们将使用在天气预测中更常见的统计方法来弄清楚亚极海洋性质和推翻如何连接到潜在的可预测的大型大气循环模式。在OSNAP观察期间，将使用将模型与观察结果结合起来的创新方法来确定对北大西洋亚大西洋的演变的最佳估计。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审查标准来评估的值得支持的。

项目成果

Distinct sources of interannual subtropical and subpolar Atlantic overturning variability

• DOI: 10.1038/s41561-021-00759-4
• 发表时间: 2021-05-31
• 期刊: NATURE GEOSCIENCE
• 影响因子: 18.3
• 作者: Kostov, Yavor;Johnson, Helen L.;Smith, Timothy
• 通讯作者: Smith, Timothy