ABSTRACT

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.

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