From September 2019 to October 2020 the icebreaker Polarstern of the Alfred Wegener Institute drifted through the Arctic Ocean as platform to facilitate interdisciplinary studies of the Arctic climate system. The mission is called “Multidisciplinary drifting Observatory for the Study of Arctic Climate” – MOSAiC. At the center of scientific activities are investigations of the sea ice, ocean, atmosphere, ecosystem and biogeochemistry.