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

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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.