Collaborative research: Quantifying Global and Regional Impacts of the Atlantic Meridional Overturning Circulation (AMOC) Slowdown in the 21st (twenty-first) Century

合作研究：量化 21 世纪大西洋经向翻转环流 (AMOC) 放缓对全球和区域的影响

• 批准号: 2053121
• 负责人: Wei Liu
• 金额: $ 32.5万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-15 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2053121&HistoricalAwards=false
• 关键词: Collaborative; research; Quantifying; Global; Regional

A denser liquid will sink below a lighter one just as vinegar sinks below oil in a salad dressing. This sinking effect happens in the North Atlantic around Greenland and Iceland, where warm surface water brought by the Gulf Stream cools in the subarctic climate and becomes denser than the water below it. The cold surface water sinks to great depth where it flows slowly southward, circulating throughout the world's oceans before resurfacing and returning to the North Atlantic. The resulting Atlantic Meridional Overturning Circulation (AMOC) moves surface water northward and deep water southward throughout the entire Atlantic basin. The AMOC transports heat northward over its whole length, not just from the warmer tropics to the colder high latitudes of the Northern Hemisphere but across the equator as well, transferring heat from the Southern Hemisphere into the Northern Hemisphere.Simulations of the response of climate to increases in greenhouse gas concentrations consistently show a slowdown of the AMOC as climate warms, a consequence of warming-induced reductions in the density of surface water in the northern North Atlantic. Density reduction is a direct consequence of warmer water temperature but reductions in saltiness also contribute, as fresh water (which is less dense) is added by melting ice sheets and increased precipitation. Also, the increased moisture content of warmer surface air reduces evaporation, and reduced evaporation means less salty surface water since evaporation removes fresh water leaving salt behind. There is observational evidence for AMOC slowdown but the period of record is somewhat short for a definitive assessment.Several climatic effects of AMOC slowdown have been claimed, including changes in precipitation over Europe, an increase in North Atlantic storms tracking into Europe, changes in the frequency and strength of El Nino events, and a southward shift in the intertropical convergence zone (ITCZ), the narrow rain band that typically sits north of the equator over the tropical oceans. Many authors have argued that the AMOC slowdown is responsible for the North Atlantic Warming Hole (NAWH), a region of minimal warming or even slight cooling found in the North Atlantic south of Greenland in most climate change simulations. A reduction in AMOC heat transport into the northern North Atlantic is a reasonable explanation for the warming hole, but it is possible to produce a NAWH in global warming simulations using a model that does not allow AMOC slowdown.Work supported through this award uses a novel methodology to examine the effects of AMOC slowdown and their connection to the NAWH using simulations from an ensemble of four climate models. The simulations use a novel methodology in which just enough salt is removed from the surface ocean in the northern North Atlantic to prevent the AMOC slowdown that would otherwise occur due to greenhouse gas-induced warming. A preliminary simulation performed with a version of the Community Earth System Model (CESM) produces the NAWH as a consequence of AMOC slowdown, along with a reduction in rainfall over the warming hole and several other climatic impacts. But results from a single model are not definitive given that differences in model formulation can lead to substantial differences in model behavior. The project also includes a detailed examination of the mechanisms through which AMOC slowdown causes local and remote responses.The work has societal relevance due to the human impacts of climate change and the need to help decision makers confronting climate change. The Principal Investigators conduct outreach activities at two museums, the Museum of Riverside and the Peabody Museum of Natural History, including public lectures and symposia as well as teacher development workshops. The project supports a graduate student and a postdoctoral fellow, thereby supporting workforce development in this research area.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.

浓密的液体会下沉较轻的液体，就像醋在沙拉酱中下沉在油下一样。 这种下沉效应发生在格陵兰和冰岛周围的北大西洋，海湾溪流带来的温暖地表水在亚北极气候中冷却，并且比下面的水变得浓密。 冷的地表水沉入了深度，在那里缓慢地向南流动，在重新铺面并返回北大西洋之前，在世界的海洋中循环。由此产生的大西洋子午翻转循环（AMOC）在整个大西洋盆地中向南和深水向南移动地表水。 AMOC在整个长度上向北运输热量，不仅从较温暖的热带到北半球的较冷高纬度，而且还穿过赤道，从南半球转移热量到北半球，象征着气候的响应速度逐渐变暖，这是一种稳定的层次，这是一种稳定的效果 - 一致地表现出温暖的状态，这是一种升温，这是一个升高的状态，这是一种暖气，这是一种暖气，这是一种暖气，这是一种稳定的状态，这是一种暖气，这是一种良好的状态，这是一种升高的状态，这是一个稳定的效果，这是一种升高的状态，这是一个稳定的状态，这是一个稳定的状态，这是一种良好的状态，这是一个升高的状态，这是一个稳定的效果，这是一个温暖的状态，这是一个稳定的效果，这是一个稳定的状态。北大西洋北部的水。 密度降低是水温较高的直接结果，但盐度的降低也会促进，因为淡水（较少密度）是通过熔化的冰盖和增加的降水而增加的。同样，温暖地面空气的水分含量增加可减少蒸发，减少蒸发意味着较少的咸地表水，因为蒸发消除了淡水留下盐。 There is observational evidence for AMOC slowdown but the period of record is somewhat short for a definitive assessment.Several climatic effects of AMOC slowdown have been claimed, including changes in precipitation over Europe, an increase in North Atlantic storms tracking into Europe, changes in the frequency and strength of El Nino events, and a southward shift in the intertropical convergence zone (ITCZ), the narrow rain band that typically sits north of the equator over the tropical海洋。 许多作者认为，AMOC放缓是北大西洋暖洞（NAWH）的原因，这是在大多数气候变化模拟中，在格陵兰岛北大西洋南部的最小变暖甚至少量冷却。 对变暖洞的AMOC热传输的减少是一个合理的解释，但是使用不允许AMOC放缓的模型，可以在全球变暖模拟中产生NAWH。通过该奖项支持的工作使用AMOC速度减速的新方法来检查AMOC速度减速及其与NAWH与NAWH的效果，并使用四个气候模型的模拟对NAWH的连接。 模拟使用一种新型方法，其中将足够的盐从北大西洋北部的地面海洋中除去，以防止AMOC放缓，否则由于温室气体引起的变暖而发生。 使用社区地球系统模型（CESM）进行的初步模拟，由于AMOC放缓而产生NAWH，并减少了温暖孔的降雨量以及其他几种气候影响。但是，鉴于模型公式的差异会导致模型行为的实质性差异，但单个模型的结果并不确定。 该项目还包括对AMOC降低引起本地和远程响应的机制的详细检查。由于气候变化的人类影响以及帮助决策者面对气候变化的需求，这项工作具有社会意义。 首席调查人员在两个博物馆，里弗赛德博物馆和皮博迪自然历史博物馆进行外展活动，包括公开讲座和座谈会以及教师发展研讨会。 该项目支持研究生和博士后研究员，从而支持该研究领域的劳动力发展。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的评估审查标准来通过评估来支持的。

项目成果

The Impacts of a Weakened Atlantic Meridional Overturning Circulation on ENSO in a Warmer Climate

• DOI: 10.1029/2023gl103025
• 发表时间: 2023-04
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Wei Liu;David Duarte Cavalcante Pinto;A. Fedorov;Jiang Zhu

The Role of a Weakened Atlantic Meridional Overturning Circulation in Modulating Marine Heatwaves in a Warming Climate

• DOI: 10.1029/2021gl095941
• 发表时间: 2021-11
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Xianglin Ren;Wei Liu

Interaction between Arctic sea ice and the Atlantic meridional overturning circulation in a warming climate

• DOI: 10.1007/s00382-021-05993-5
• 发表时间: 2021-10-20
• 期刊: CLIMATE DYNAMICS
• 影响因子: 4.6
• 作者: Liu, Wei;Fedorov, Alexey
• 通讯作者: Fedorov, Alexey