Climate change is an inherently global issue but changes are manifested regionally. The climate in the Arctic is changing dramatically, faster than anywhere else on Earth. This project will answer questions on the sensitivity and fate of the Arctic climate: “Are we on an irreversible path towards an ice-free Arctic summer, even with reasonable global climate stabilization?” An ice-free Arctic has serious implications for life north of the Arctic Circle and research suggests that lower latitudes would also be affected. The societal and economic effects are global. With new observations, coupled to unique modeling capabilities, we will determine and quantify the main processes responsible for the observed rapid Arctic change, enabling projections of the fate of the future Arctic climate.