The fast-changing Arctic climate is determined by a balance between heat imported from the south, most of it in the atmosphere, and energy lost to space by radiation at the top of the Arctic atmosphere. The expedition ARTofMELT2023 (Atmospheric Rivers and the Onset of Sea Ice Melt 2023), led by researchers from Stockholm University has collected unique observations of the processes that govern the transition from winter to summer in the high Arctic, the time when the Arctic ice starts melting.