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

我们假设大西洋经向翻转环流（AMOC）是控制北方半球天气和气候的一个因素。从原因（AMOC）到结果（天气/气候控制）的推理由三个组成部分组成，而这三个组成部分又是本提案的重点。(1)极端大气事件通过对风暴路径的巨大但罕见的贡献来控制平均大气场。(2)这些极端的大气事件是由与墨西哥湾流（GS）的热交换，是敏感的GS是在蜿蜒或非蜿蜒状态。(3)GS的（非）蜿蜒状态响应于AMOC变异性。本文通过对北大西洋墨西哥湾流（GS）海气系统的数值-观测研究，支持或反驳这一假说。墨西哥湾流（GS）在调节北方天气和气候中的作用最近得到了相当多的支持。感兴趣的部分在于与大气相比，GS变化的相对持久性，这提供了增加灾难性天气事件的可预测性的潜力。观测结果表明，GS蜿蜒每月的时间尺度显着的变化。最近的观测实验也证实了AMOC在这些月度时间尺度上的高度可变性。这提供了AMOC和中纬度天气之间通过GS的潜在联系。然而，模型研究尚未就AMOC和GS之间的关系达成一致。造成这些差异的原因有很多，但最重要的解释似乎是涡旋尺度分辨率（< 1/10 o）。我们在佛罗里达州立大学，在先前的国家科学基金会的资助下，已经产生了一个涡流解决北大西洋模拟，由于其建设，似乎是理想的设计，以解决上述问题。事实上，目前，这是美国唯一的北大西洋模式模拟的涡解集合套件。我们建议利用这些运行系统地评估AMOC和GS变化与海洋涡旋的影响明确解决之间的关系。我们的重点将主要放在那些墨西哥湾流的属性，已被证明显着影响当地和全球的大气。此外，额外的模拟工作将评估AMOC的变化如何通过其对GS变异性的影响而对大气产生影响。这将通过在高分辨率的大气模型模拟中规定GS条件来实现，以系统地评估大气变率和地表热通量对底层海洋的依赖性。最后，将进行高分辨率的耦合运行，以阐明大气反馈对海洋的贡献。

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.