Rapid Adjustments and Their Effects on Arctic Amplification

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Arctic amplification (AA) refers to the enhanced warming of the Arctic relative to lower latitudes. Understanding the physical processes that give rise to AA is critical, given its impacts on a range of human and natural systems. This project tests the hypothesis that fast atmospheric processes – known as “rapid adjustments” – are fundamental to the occurrence of AA. This represents a new way of thinking about AA, which has traditionally been attributed to much slower processes such as sea-ice loss. The project thus will enhance our understanding of AA and its underlying physical mechanisms, and also has the potential to fundamentally reshape how we view this phenomenon. Broader impacts of the project will include the development of a new curriculum on climate modeling that will be suitable for use in high school Earth science or physics courses.Despite intense scientific scrutiny, the relative importance of different physical processes in driving Arctic amplification (AA) remains uncertain. Most studies to date to understand these processes have focused on long time scales (e.g., multidecadal and longer). This project, in contrast, focuses on the short time scales of AA. More specifically, the project will test the hypothesis that rapid adjustments to external forcing – which are the response to the forcing that is independent of global mean surface temperature change – are fundamental to the occurrence of AA. This hypothesis will be tested by analyzing a series of new and existing global climate model (GCM) simulations. The project will provide the most systematic investigation to date of the role of rapid adjustments in AA, potentially transforming current understanding of AA and its underlying physical mechanisms. The project will also enhance understanding of rapid adjustments more generally, including how they differ between CO2 and non-CO2 forcings, and how they depend on the method used to define them (e.g., “Gregory” regression versus fixed sea surface temperature GCM simulations). The new GCM simulations created for the project will be made freely available to the scientific community, thus contributing to scientific discovery beyond the scope of the project.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.