The Impact of Arctic Amplification on the Midlatitude Circulation: Non-linearity and Non-additivity

北极海冰损失和北极表面快速变暖（与北极放大有关）对北半球大气环流的影响尚不完全清楚。随着海冰损失的加剧，对大气环流、急流和极端天气事件的影响是否会加剧？不同北极地区的海冰损失是否使北极放大的影响复杂化？该提案解决了这些问题，并旨在促进目前对北极海冰融化和北极放大对高影响极端天气影响的理解。新出现的结果可以提高这些极端事件的可预测性，这些事件对交通和能源生产实践的规划和管理具有重大的社会影响。该项目将培训和支持一名研究生和两名本科生暑期实习生，后者通过暑期项目重点招收代表性不足的社区大学生。研究小组假设：(1)大气阻塞和极端天气对北极海冰损失和变暖的响应是非线性的：当北极强迫强度较小时，阻塞的频率和局部持续时间随着强迫的增加而增加；但随着强迫强度的增大，阻塞度随强迫的增大而减小；(2)北极海冰融化的区域响应不是线性加性的，由于波浪-平均流的非线性相互作用，非加性分量显著。提出的任务将在从简单的干动力学表示到最先进的大气环流模型的一系列模型中检验这些假设。它将评估非线性和非可加性的鲁棒性，并使用新的诊断方法（如局部有限振幅波活动）检查潜在的动力机制。该研究将对大气阻塞和极端天气变化背后的大尺度大气环流模式提供系统的、面向过程的动力学理解，并促进未来气候和大尺度动力学研究领域的劳动力和多样性。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 impact of Arctic sea-ice loss and rapid surface warming over the Arctic (associated with Arctic Amplification) on the atmospheric circulation in the Northern Hemisphere is not fully understood. As the sea-ice loss worsens, does the effect on the atmospheric circulation, jet stream, and extreme weather events intensify? Does the different sea-ice loss over various Arctic regions complicate the influence of Arctic Amplification? This proposal addresses these questions and aims to advance the current understanding of the impact of the Arctic sea-ice melting and Arctic Amplification on high-impact weather extremes. The emerging results can improve the predictability of these extreme events that have significant societal impacts in the planning and management of transportation and energy production practices. The project will train and support a graduate student and two undergraduate summer interns, the latter through a summer program focused on the recruitment of underrepresented and community college students.The investigative team hypothesizes that (1) atmospheric blocking and weather extremes respond to Arctic sea ice loss and warming non-linearly: when the Arctic forcing magnitude is small, the frequency and local persistence of blocking increases with forcing; however, as the forcing magnitude becomes large, blocking decreases with forcing; (2) responses to regional Arctic sea ice melting are not linearly additive and the non-additivity component is significant due to the nonlinear wave-mean flow interaction. The proposed tasks will test these hypotheses in a hierarchy of models ranging from a simple dry dynamics representation to a state-of-the-art atmospheric general circulation model. It will assess the robustness of non-linearity and non-additivity and examine the underlying dynamical mechanism using novel diagnostics such as the local finite-amplitude wave activity. The research will provide a systematic and process-oriented dynamical understanding of the large-scale atmospheric circulation patterns underlying the changes in atmospheric blocking and weather extremes and promote the future workforce and diversity in the research area of climate and large-scale dynamic.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.