Article Open access Luisa von Albedyll , H. Jakob Bünger , Giulia Castellani , Jörg Hartmann , Veit Helm , Stefan Hendricks , Nils Hutter , Jack C. Landy , Simeon Lisovski , Christof Lüpkes , Jan Rohde , Mira Suhrhoff & Christian Haas Nature Climate Change (2025) Cite this article Metrics Abstract Pressure ridges, formed by sea ice deformation, affect momentum transfer in the Arctic Ocean and support a larger biomass than the surrounding-level ice. Although trends in Arctic sea ice thickness and concentration are well documented, changes in ridge morphology remain unclear. This study provides airborne-based evidence of a shift towards a smoother ice surface, with fewer pressure ridges and reduced surface drag, attributed to the loss of old ice. Furthermore, an increase in seasonal ice cover enhances overall deformation in the Arctic and acts as a negative feedback mechanism on pan-Arctic ridge morphology: the greater the proportion of seasonal ice, the higher the pan-Arctic mean ridge rate, dampening an overall decline in ridges with age. While thinner and less frequent ridges benefit industries such as shipping, these changes are likely to have profound impacts on the energy and mass balance and the ecosystem of the Arctic Ocean. Main Driven by wind and ocean currents, sea ice exhibits a dynamic nature 1 . This constant movement fosters convergence and shear among the ice masses, leading to the formation of pressure ridges—distinct and elevated features with sails and keels, disrupting the otherwise level sea ice surface 2 . Pressure ridges have a pivotal role in the Arctic environment, influencing the energy 3 and mass balance of sea ice 4 , as well as the biogeochemical cycle and the ecosystem 5 . The portion above the water line, the sails, facilitates momentum transfer from the atmosphere into the ocean […]