The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) will be the first year-round expedition into the central Arctic exploring the Arctic climate system. The results of MOSAiC will contribute to enhance understanding of the regional and global consequences of Arctic climate change and sea-ice loss and improve weather and climate predictions. As such it will support safer maritime and offshore operations, contribute to an improved scientific basis for future fishery and traffic along northern sea routes, increase coastal-community resilience, and support science-informed decision-making and policy development. Improved understanding of the impact of Arctic climate change on conditions world-wide will provide stakeholders and decision-makers with improved knowledge for adapting to climate change and develop target oriented mitigation strategies. The Federal Ministry of Education and Research BMBF provides the base budet for the Alfred-Wegener-Institute as leading research insitute including the RV "POLARSTERN" in support of the project.