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

我们假设大西洋子午线翻转环流(AMOC)是对北半球天气和气候的控制。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气压场。(2)这些极端大气事件受与墨西哥湾流(GS)的热量交换控制，对GS处于曲折状态还是非曲折状态很敏感。(3)GS的(非)曲折状态响应于AMOC的变化。本文通过对北大西洋湾流上空海洋-大气系统的数值-观测研究来支持或驳斥这一假说。墨西哥湾流在调节北半球天气和气候方面的作用最近得到了相当大的支持。人们的兴趣部分在于与大气相比，GS变率的相对持久性，这为提高灾难性天气事件的可预测性提供了可能性。观测表明，GS在每月时间尺度上的曲折变化显著。最近的观测实验也证实了AMOC在这些月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涉及(缺乏)涡旋尺度分辨率(&lt；1/10o)。我们在佛罗里达州立大学，在之前的NSF资助下，已经生成了一组涡流解析北大西洋模拟，由于它们的构建，似乎是为解决上述问题而设计的理想方案。事实上，这是目前美国唯一的北大西洋模式模拟涡旋分辨系综。我们建议利用这些运行来系统地评估AMOC和GS可变性之间的关系，并明确解决海洋涡旋的影响。我们的重点将主要放在那些已被证明对当地和全球大气产生重大影响的墨西哥湾流属性上。此外，额外的模拟工作将评估AMOC的变化如何通过其对GS可变性的影响而影响大气。这将通过在仅限大气的高分辨率模式模拟中规定GS条件来实现，以系统地评估大气可变性和表面热通量对下层海洋的依赖。最后，将进行耦合的高分辨率运行，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.