NSFGEO-NERC:Assessing the influence of sub-annual variability in the Atlantic Meridional Overturning Circulation on the Gulf Stream and the atmosphere

NSFGEO-NERC：评估大西洋经向翻转环流的亚年变率对墨西哥湾流和大气的影响

• 批准号: NE/V014897/1
• 负责人: Arnaud Czaja
• 金额: $ 30.86万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FV014897%2F1
• 关键词: NSFGEO; NERC; Assessing; influence; sub

We hypothesize that the Atlantic Meridional Overturning Circulation (AMOC) is a control on weather and climate in the Northern Hemisphere. The reasoning leading from the cause (AMOC) to effect (weather/climate control) consists of three components which, in turn, are the foci of this proposal. (1) Extreme atmospheric events control mean atmospheric fields through anomalously large, but rare, contributions to the storm track. (2) These extreme atmospheric events are governed by heat exchange with the Gulf Stream (GS), and are sensitive to whether the GS is in a meandering or non-meandering state. (3) The (non)-meandering state of the GS responds to AMOC variability. We propose here to support or refute this hypothesis by means of a combined numerical-observational study of the ocean-atmosphere system over the North Atlantic Gulf Stream.The role of the Gulf Stream (GS) in modulating the weather and climate of the Northern Hemisphere has received considerable recent support. Interest in part lies in the relative persistence of GS variability compared to the atmosphere, which offers the potential for increased predictability of catastrophic weather events. Observations show significant variability in GS meandering on monthly timescales. Recent observational experiments have also confirmed a high degree of variability in the AMOC on these monthly timescales. This provides a potential connection between the AMOC and mid-latitude weather via the GS. Modelling studies, however, have yet to agree on the relationship between the AMOC and the GS. There are many causes for these discrepancies, but an overarching explanation appears to involve (the lack of) eddy-scale resolution (< 1/10o). We here at Florida State University, under prior NSF funding, have generated an ensemble of eddy resolving North Atlantic simulations that, due to their construction, appear to be ideally designed to address the above issues. In fact, currently, this is the only eddy-resolving ensemble suite of North Atlantic model simulations in the United States. We propose to leverage these runs to systematically evaluate the relationship between the AMOC and GS variability with the influence of ocean eddies explicitly resolved. Our focus will primarily be on those Gulf Stream attributes that have been shown to significantly influence the atmosphere locally and globally. Furthermore, additional modelling work will assess how changes in the AMOC, through its influence on GS variability, imprint on the atmosphere. This will be achieved by prescribing GS conditions in high-resolution atmosphere-only model simulations to systematically assess the dependence of atmospheric variability and surface heat fluxes on the underlying ocean. Lastly, coupled high-resolution runs will be conducted to elucidate the contribution of atmospheric feedbacks on the ocean.

我们假设大西洋经向翻转环流（AMOC）对北半球的天气和气候具有控制作用。从原因（AMOC）到结果（天气/气候控制）的推理由三个部分组成，而这三个部分又是本提案的重点。(1)极端大气事件通过异常大但罕见的对风暴路径的贡献来控制平均大气场。(2)这些极端大气事件受与墨西哥湾流（GS）的热交换控制，对墨西哥湾流是否处于蜿蜒或非蜿蜒状态敏感。(3)地表（非）蜿蜒状态响应AMOC的变异。我们在此建议通过对北大西洋湾流的海洋-大气系统的数值-观测联合研究来支持或反驳这一假设。墨西哥湾流（GS）在调节北半球天气和气候方面的作用最近得到了相当多的支持。部分兴趣在于与大气相比，GS变率的相对持久性，这为增加灾难性天气事件的可预测性提供了潜力。观测结果显示，在月时间尺度上，GS蜿蜒有显著的变异性。最近的观测实验也证实了AMOC在这些月时间尺度上的高度变化。这提供了AMOC和中纬度天气之间通过GS的潜在联系。然而，模拟研究尚未就AMOC和GS之间的关系达成一致。造成这些差异的原因有很多，但最主要的解释似乎与（缺乏）涡流尺度分辨率（< 1/ 100）有关。我们在佛罗里达州立大学，在国家科学基金会的资助下，已经生成了一个涡旋解析北大西洋模拟集合，由于它们的结构，似乎是解决上述问题的理想设计。事实上，目前，这是美国唯一的解决涡旋的北大西洋模式模拟集合套件。我们建议利用这些运行来系统地评估AMOC和GS变异与明确解决的海洋涡流影响之间的关系。我们的重点将主要放在那些已被证明对当地和全球大气有重大影响的墨西哥湾流特性上。此外，额外的模拟工作将评估AMOC的变化如何通过其对GS变率的影响对大气产生影响。这将通过在高分辨率大气模式模拟中规定GS条件来实现，以便系统地评估大气变率和地表热通量对海底海洋的依赖。最后，将进行耦合高分辨率运行，以阐明大气反馈对海洋的贡献。