The CASCADES Expedition: multidisciplinary observations of a rapidly changing Arctic

 The Arctic, spanning over eight sovereign countries and the Arctic Ocean, is warming three tofour times faster than the global average, driving profound transformations of the cryosphereand ocean systems. It harbours four critical climate tipping points: the accelerated melt of theGreenland Ice Sheet, the thawing of boreal permafrost, the collapse of winter Arctic sea ice,and the weakening of the Labrador–Irminger Seas convection. These processes are tightlyinterconnected and play a key role in regulating the global climate, yet their combined impactsremain insufficiently constrained by observations.Within this context, the CASCADES Expedition is an international and interdisciplinary polarprogramme designed to investigate the coupled interactions between glaciers, sea ice, and theocean around Baffin Bay and Northwest Greenland. CASCADES is coordinated by the InstitutNordique du Québec, the Swiss Polar Institute, and the French Polar Institute, in collaborationwith Greenlandic institutions. It brings together more than 50 Canadian, French, Greenlandic,and Swiss researchers around 16 scientific projects from 13 research institutions.CASCADES will be conducted aboard the Canadian research icebreaker CCGS Amundsen andis structured into two complementary legs in 2026, aligned with critical seasonal phases of theArctic system. A first leg during the summer targets peak glacier melt and freshwater input,while a second leg during autumn focuses on the transition toward sea-ice freeze-up. This dual-season strategy enables the investigation of how physical, chemical, and biological processesevolve from melt to freeze-up, and how these transitions affect carbon cycling, productivity,and ecosystem structure.By providing coordinated, multidisciplinary observations across key Arctic seasons,CASCADES aims to improve understanding of cryosphere–ocean–ecosystem coupling and itsimplications for the North Atlantic and the global climate system. Beyond its core scientificobjectives, the expedition serves as a platform for international collaboration, sciencediplomacy, education, and engagement with Arctic communities, contributing to sharedobservation efforts and to the anticipation of climate-driven changes in polar oceans and beyond.