The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) is an international Arctic research initiative that is broadly motivated by the dramatic changes in the Arctic climate system over the last few decades, highlighted by significant losses of sea ice, and generally deficient model representations of the important processes responsible for, and responding to, these changes. The ultimate goal of the initiative is to enhance understanding of central Arctic coupled atmosphere-­‐ice-­‐ocean-­‐ecosystem processes to improve numerical models for sea ice forecasting, extended-­‐range weather forecasting, climate projections, and climate change assessment.