Collaborative Research: Understanding the impact of Arctic sea ice loss on summertime climate change

北极海冰的减少是世界正在变暖的戏剧性证据，因为融化季节结束时的海冰覆盖面积已从1980年的约700万平方英里下降到2022年的约500万平方英里。 冰盖的减少会产生变暖效应，因为冰盖的减少会暴露出更暗的海洋表面，使海洋吸收更多的阳光。这种变暖对北极圈以下天气和气候的影响是一个非常感兴趣的话题，因为北极变暖可以通过削弱急流并将其向南转移来影响中纬度天气。 迄今为止，大多数研究都集中在冬季的影响上，特别是在冷空气爆发和暴风雪方面。 但PI和其他人最近的研究表明，急流的减弱也可能发生在夏季，导致沿着中纬度风暴路径行进的气旋和反气旋减弱。 研究结果还表明，类似的效应也可以作为温室气体引起的大气变暖的直接反应而发生，因此需要努力分离出海冰减少的影响。本项目针对海冰减少对夏季大气环流的影响，提出了四个问题：1）北极海冰减少在多大程度上影响夏季大气环流，通过什么机制影响夏季大气环流？ 2)对夏季循环的影响何时会变得明显？ 3)与大气变暖对夏季环流的直接影响相比，海冰减少的影响如何？4)北极海冰减少对热浪的影响是什么？热浪的影响与环流变化有何关系？该研究是通过分析在探测和归因模型相互比较项目（DAMIP）和极地放大模型相互比较项目（PAMIP）中生成的气候模型模拟，以及使用社区地球系统模型（CESM）专门为该项目创建的模拟来进行的。 为该项目创建的模拟旨在显示北极海冰减少和大气温室效应造成的不同反应。 为该项目开发的一种分析方法将海冰减少对气旋的影响与其对反气旋的影响分开，这一点很有意义，因为反气旋与夏季热浪有关，这项工作具有社会和科学意义，因为需要为气候变化的后果做好准备和适应。 北极海冰减少对大气环流和相关极端天气可能产生的影响已引起科学界和媒体的极大关注，因此，非常需要对海冰减少的可能后果有更好的基础科学了解。 该项目还将提供支持和培训，以研究生，并通过领导联盟，一个组织，以促进更高层次的教育和研究的多样性招募一名本科生。这个奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

The decline of Arctic sea ice is dramatic evidence that the world is warming, as sea ice cover at the end of the melt season has fallen from about 7 million square miles in 1980 to about 5 million in 2022. The loss of ice cover has a warming effect as ice loss exposes the darker ocean surface allowing the ocean to absorb more sunlight. The influence of this warming on weather and climate below the Arctic circle is a topic of great interest, as Arctic warming can influence midlatitude weather by weakening the jet stream and shifting it southward. Most of the research to date has focused on the effect in winter, looking in particular at cold air outbreaks and snowstorms. But recent work by the PI and others suggests that the weakening of the jet stream could also happen in summer, resulting in a weakening of the cyclones and anticyclones that travel along the storm tracks of the middle latitudes. The work also shows that similar effects can occur as a direct response to the warming of the atmosphere by greenhouse gases, thus some effort is required to separate out the effects of sea ice decline.This project addresses the effects of sea ice decline on atmospheric circulation in summer, addressing four questions: 1) To what extent does Arctic sea ice loss affect summer atmospheric circulation, and through what mechanisms? 2) When will the effects on summer circulation become evident? 3) How does the impact of sea ice decline compare to the direct effect of atmospheric warming on summer circulation? 4) What is the effect of Arctic sea ice decline on heat waves and how are the heat waves effects related to the circulation changes?The research is conducted through analysis of climate model simulations generated in the Detection and Attribution Model Intercomparison Project (DAMIP) and the Polar Amplification Model Intercomparison Project (PAMIP), as well as simulations created specifically for the project using the Community Earth System Model (CESM). Simulations created for the project are designed to show the separate responses forced by Arctic sea ice decline and the greenhouse warming of the atmosphere. One analysis method developed for the project separates the effects of sea ice decline on cyclones from its effects on anticyclones, which is of interest as anticyclones are associated with summer heat waves.The work is of societal as well as scientific interest given the need to prepare for and adapt to the consequences of climate change. The possible effect of Arctic sea ice loss on atmospheric circulation and related extreme weather has attracted considerable attention, both in the scientific community and the media, thus better basic science understanding of the likely consequences of sea ice decline is highly desirable. The project would also provide support and training to a graduate student and recruit an undergraduate student through the Leadership Alliance, an organization created to promote diversity in higher-level education and research.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.