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.

该项目由美国国家科学基金会地球科学理事会 (NSF/GEO) 和英国国家环境研究理事会 (NERC) 通过 NSF/GEO-NERC 牵头机构协议共同资助。该协议允许美国/英国的单一联合提案由其调查人员拥有最大预算比例的机构提交并进行同行评审。在成功联合确定资助后，每个机构将资助与其本国相关的预算和调查人员的比例。副极地北大西洋位于英国、格陵兰岛和加拿大之间，在当地和全球气候中发挥着至关重要的作用。这是一个关键区域，在北大西洋上部向北流动的大部分暖水将热量释放到大气中，并转化为寒冷、稠密的水，然后在所谓的大西洋翻转环流中再次向南深处流动。这种环流携带大量热量向北释放到大气中，影响风暴的路径并决定西欧的天气。翻转环流还通过影响低纬度海面温度，对非洲降雨和飓风发展产生深远影响。此外，副极地地区水的下沉使深海通风，将热量和碳从表面转移出去，并减轻人为温室气体对表面温度的影响。任何在副极地地区不下沉的温水都会再循环或将其热量进一步向北带到北极，在下沉和向南流动之前影响海冰条件和极地海洋生态系统。这项研究旨在使我们对将大气变化与副极地海洋变化联系起来的过程、它们对该地区海洋和气候可预测性的影响，以及我们对它们在气候模型中的表示的信任程度产生重大影响。最近，副极地北大西洋翻转计划（OSNAP，www.o-snap.org）对北大西洋副极地翻转环流进行了首次观测。这些揭示了倾覆的大幅变化，并对引起这种变化的位置和过程及其对表面海洋条件和气候可能产生的影响提出了疑问。在气候模型中正确代表该地区对于在季节、年际、年代际和更长的时间尺度上做出有用的气候预测至关重要。然而，当前一代的模型很难代表已知的重要过程，并且与对温水转化为浓水位置的观察结果不一致。这些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的性能，因为对大气条件和海洋环流变化之间的所有联系的了解有限。该项目将把 OSNAP 和其他观测结果与能够代表小规模过程的数值模型结合起来，以揭示副极地海洋环流变化的原因。一旦明确哪些过程最重要以及它们如何运作，团队将能够确定哪些气候模型出了问题并提出改进建议。这将改善对北大西洋副极地及其他地区海洋和气候变化的预测。研究小组将调查寒冷、稠密的海水如何进入边界流并将其输送到南方。它将确定风所扮演的角色，这可能比我们过去假设的更为复杂，并将确定北极和格陵兰岛淡水出口变化对颠覆性变化的影响。为了表征和量化这些关键过程，除了使用海洋观测之外，研究人员还将执行“如果？”海洋模型实验，提出以下问题：如果大西洋上空的大气急流发生变化或加强，副极地海洋环流会发生什么？他们将使用天气预报中更常见的统计方法来弄清楚副极地海洋特性和翻转如何与潜在可预测的更大规模的大气环流模式联系起来。将模型与观测相结合的创新方法将用于确定 OSNAP 观测期间北大西洋副极地演变的最佳估计。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

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