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: 2038449
• 负责人: Xiaobiao Xu
• 金额: $ 12.73万
• 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: 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=2038449&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委员会（NERC）通过NSF/GEO-NERC牵头机构协议共同资助。该协议允许美国/英国提交一份联合提案，并由其调查员拥有最大比例预算的机构进行同行评审。在成功地共同确定一项奖励后，每个机构为预算的比例和与本国有关的调查人员提供资金。位于英国、格陵兰岛和加拿大之间的亚极地北大西洋对当地和全球气候都起着至关重要的作用。这是北大西洋上层向北流动的大部分温水向大气释放热量并转化为寒冷、稠密的水的关键区域，然后再次向南流动，形成所谓的大西洋翻转环流。这种环流向北携带并释放到大气中的大量热量影响了风暴的轨迹，并决定了西欧的天气。翻转环流通过对低纬度海表温度的影响，对非洲降雨和飓风的发展也有深远的影响。此外，亚极地地区的海水下沉为深海通风，将热量和碳从地表转移出去，并减缓了人为温室气体对地表温度的影响。在亚极地地区没有下沉的任何温水都会再循环或将其热量向北带到北极，在它下沉并向南流动之前影响海冰状况和极地海洋生态系统。这项研究的目的是在我们对大气变化与亚极地海洋变率之间联系的过程、它们对该地区海洋和气候可预测性的影响以及我们在气候模式中对它们的表征的信任程度的理解上产生一个阶段性的变化。最近，北大西洋次极翻转项目（overturning in the subpolar North Atlantic Program, osap, www.o-snap.org）首次观测到了北大西洋次极翻转环流。这些发现揭示了翻转过程中的大幅度变化，并提出了关于引起这种变化的位置和过程及其对海洋表面条件和气候的可能影响的问题。在气候模式中适当地表示这一区域对于在季节、年际、年代际和更长的时间尺度上进行有用的气候预测至关重要。然而，目前这一代的模型很难表现出已知的重要过程，并且与在温水转变为致密水的地点的观测结果不一致。这些分歧限制了我们对模型预测的信心。科学界无法恰当地评估模式的性能，因为对大气条件和海洋环流变异性之间的所有联系了解有限。该项目将把ocap和其他观测资料与能够代表小尺度过程的数值模式结合起来，以揭示亚极地海洋环流变化的原因。一旦弄清楚哪些过程是最重要的，以及它们是如何工作的，该团队将能够确定哪些气候模型出错了，并提出改进建议。这将改进对北大西洋次极地及其他地区海洋和气候变化的预测。科考队将调查寒冷稠密的海水是如何进入向南输出的边界流的。它将确定风所扮演的角色，这可能比我们过去所假设的更复杂，它将决定对北极和格陵兰岛淡水输出的颠覆性变化的影响。为了描述和量化这些关键过程，除了利用海洋观测外，研究人员还将在海洋模型中进行“如果”实验，提出诸如：如果大西洋上空的大气急流转移或加强，亚极地海洋环流会发生什么？他们将使用在天气预报中更常见的统计方法来弄清楚亚极地海洋特性和倾覆如何与潜在可预测的更大规模大气环流模式联系起来。将采用将模式与观测相结合的创新方法，确定在opsnap观测期内对北大西洋次极区演变的最佳估计。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。