Most human activity in the Arctic takes place along permafrost coasts, making them a key interface. They have become one of the most dynamic ecosystems on Earth because permafrost thaw is now exposing these coasts to rapid change: change that threatens the rich biodiversity, puts pressure on communities that live there and contributes to the vulnerability of the global climate system. NUNATARYUK will determine the impacts of thawing coastal and subsea permafrost on the global climate, and will develop targeted and co-designed adaptation and mitigation strategies for the Arctic coastal population. NUNATARYUK brings together world-leading specialists in natural science and socio-economics to: (1) develop quantitative understanding of the fluxes and fates of organic matter released from thawing coastal and subsea permafrost; (2) assess what risks are posed by thawing coastal permafrost, to infrastructure, indigenous and local communities and people’s health, and from pollution; (3) use this understanding to estimate the long-term impacts of permafrost thaw on global climate and the economy. NUNATARYUK will be guided by a Stakeholders’ Forum of representatives from Arctic coastal communities and indigenous societies, creating a legacy of collaborative community involvement and a mechanism for developing and applying innovative evidence-based interventions to enable the sustainable development of the Arctic.