A3M-transform · Understanding Arctic amplification of climate change through air-mass transformations

We expect that temperatures over the wintertime central Arctic will increase by 20 degrees - and precipitation will double - by the end of this century if greenhouse gas emissions continue to rise. Arctic sea-ice is projected to completely melt in summer within the next decades, and may cease to form in winter in the coming century. The traditional framework to understand this Arctic amplification of climate change focuses on the steady-state mean Arctic climate. However, the Arctic wintertime atmosphere has two preferred states that are largely controlled by initially warm and moist air masses that cool and dry after being advected from lower latitudes. We understand little about how these air masses cool and dry, and what controls the sudden transition from a cloudy state to a clear state along their trajectory. This lack of understanding is a major obstacle to scientific progress and improved climate models. To achieve groundbreaking progress, I will analyze the warm, moist poleward flows, cold, dry equatorward flows and the air-mass transformations that lead from one to the other. I will observe and model such air masses along their trajectories using recently developed air-mass following balloons and customized model setups. Cooling of air in the Arctic mirrors heating in the Tropics. Together, these drive the global atmospheric circulation, but the Arctic’s role in this picture has largely been overlooked. My team will investigate how the Arctic couples to the global climate system using a novel concept of averaging the atmospheric circulation. We will focus on how and why both the heat and moisture content and the amount of air transported into and out of the Arctic change in a warming world and contribute and respond to Arctic amplification.A3M-transform will deliver a step change in understanding the air-mass transformation processes that shape Arctic amplification and transform our view of how the Arctic couples to the global climate system.