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有力证据，因为海冰覆盖面积在融化季节结束时已从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，因为冰层的减少会使深色的海洋表面暴露出来，从而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有趣的话题，因为北极变暖可以通过削弱急流并使其向南移动来影响中纬度地区的天气。迄今为止，大多数研究都集中在冬季的影响上，特别是关注冷空气爆发和暴风雪。但是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，导致沿中纬度风暴路径行进的气旋和反气旋减弱。这项工作还表明，类似的影响可能作为温室气体导致大气变暖的直接反应而发生，因此需要做出一些努力来分离海冰减少的影响。本项目研究海冰减少对夏季大气环流的影响，主要解决四个问题：1)北极海冰减少对夏季大气环流的影响程度和影响机制；2)对夏季环流的影响何时显现？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？该研究通过分析探测与归因模式比对项目（DAMIP）和极地放大模式比对项目（PAMIP）产生的气候模式模拟，以及使用社区地球系统模型（CESM）为该项目专门创建的模拟来进行。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变暖所造成的不同反应。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，这一点很有趣，因为反气旋与夏季热浪有关。鉴于需要为气候变化的后果做好准备和适应，这项工作具有社会和科学意义。北极海冰损失对大气环流和相关极端天气的可能影响已经引起了科学界和媒体的相当大的关注，因此，对海冰减少的可能后果有更好的基础科学认识是非常可取的。该项目还将通过领导力联盟（Leadership Alliance）为一名研究生提供支持和培训，并招募一名本科生。领导力联盟是一个旨在促进高等教育和研究多样性的组织。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.