MOSAiC Expedition

The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC, /ˌməʊˈzɛɪɪk/) expedition was a one-year-long expedition into the Central Arctic (September 2019 - October 2020). For the first time a modern research icebreaker was able to operate in the direct vicinity of the North Pole year round, including the nearly half year long polar night during winter. In terms of the logistical challenges involved, the total number of participants, the number of participating countries, and the available budget, MOSAiC represents the largest Arctic expedition in history.

During its one-year-long journey, the central expedition ship, the research icebreaker Polarstern from Germany's Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), was supported and resupplied by the icebreakers and research vessels Akademik Fedorov and Kapitan Dranitsyn (Russia), Sonne and Maria S. Merian (Germany) and Akademik Tryoshnikov (Russia). In addition, extensive operations involving helicopters and other aircraft were planned. In total, during the various phases of the expedition, more than 600 people were working in the Central Arctic. The international expedition, which involved more than 80 institutions from 20 countries (Austria, Belgium, Canada, China, Denmark, Finland, France, Germany, Italy, Japan, the Netherlands, Norway, Poland, Russia, South Korea, Spain, Sweden, Switzerland, the United Kingdom, and the United States), was conducted by the AWI and was led by the polar and climate researcher Markus Rex and co-led by the atmospheric researcher Matthew Shupe from the University of Colorado Boulder. MOSAiC's main goals were to investigate the complex and still only poorly understood climate processes at work in the Central Arctic, to improve the representation of these processes in global climate models, and to contribute to more reliable climate projections.

The expedition cost 140 million euros (approximately 154 million USD); half of the budget was provided by the German Federal Ministry of Education and Research (BMBF). U.S. participation was primarily supported by the National Science Foundation, which contributed roughly $24 million to the project, among the largest Arctic research initiatives the agency has ever mounted. The U.S. Department of Energy was also highly invested in the mission, funding nearly $10 million and providing the largest suite of atmospheric instruments.

In the half-year-long Arctic winter, the sea ice is too thick for research icebreakers to penetrate. Consequently, data from the Central Arctic is virtually non-existent, particularly during winter. For reaching the Central Arctic in winter, the MOSAiC expedition followed in the footstep of Fridtjof Nansen's famous expedition with the wooden sailing ship Fram in the years 1893–1896, over 125 years ago. His daring voyage showed that it was possible to let a ship drift across the polar cap, from Siberia to the Atlantic, stuck in the thick sea ice and solely driven by the forces of the natural drift of the ice. Though Nansen has demonstrated the fundamental feasibility of such an endeavour, the scientific measurements possible in his days were still quite rudimentary. During MOSAiC, for the first time the Fram's drift was repeated with a research icebreaker, equipped with a veritable arsenal of cutting-edge instruments for exploring and recording the complex climate processes in the Central Arctic.

The heart of MOSAiC was the Polarstern's one-year-long drift through the Central Arctic. On 20 September 2019 the ship departed from the Norwegian port of Tromsø together with the Akademik Fedorov, proceeded east along the Siberian coast, and at roughly 125° East, turned north and began breaking into the sea ice of the Central Arctic, which was still feasible at that time of year. On 4 October 2019, at a position of 85° North and 134° East, the MOSAiC expedition found a suitable ice floe, which measured roughly 2.5 by 3.5 kilometres. Polarstern put her engines in neutral and allowed herself to become trapped in the sea ice. An extensive research camp was then set up all around the ship on the ice. At the same time, Akademik Fedorov deployed a network of research stations on the ice, some as far as 50 km from Polarstern's position. The network consisted of both autonomous and remote-controlled instruments, which were checked at regular intervals using helicopter flights from the central Polarstern, which formed the Central Observatory.

After delivering one last load of fuel, at the end of October Akademik Fedorov returned to Tromsø. From this point on, the natural drift carried Polarstern and its network of research stations across the North Pole region. On 24 February 2020, the Polarstern has broken a record: during the drift she reaches 88°36' North, just 156 kilometres from the North Pole. In summer 2020, the ship reached the Fram Strait. On 13 August, after a last big refueling and personnel rotation, Polarstern started steaming towards the Central Arctic to study the onset and early freezing phase of the sea ice. On 19 August, the ship reached the North Pole. The journey from the northern Fram Strait to the Pole only took six days to complete. After a short search, the MOSAiC team found a new ice floe. The so-called MOSAiC floe 2.0 was discovered eleven nautical miles from the route that the original floe took in January 2020. Polarstern left the MOSAiC floe 2.0 on 20 September 2020, one year after the start of the expedition. On 12 October 2020, the Polarstern returned to her homeport in Bremerhaven.

During the period August/September 2020, the German research aircraft Polar 5 and Polar 6 took off from Spitsbergen to conduct aerial surveys of the sea ice and atmosphere over the Arctic Ocean, supplementing the MOSAiC expedition's research programme.

Fuel depots set up on islands off the coast of Siberia specifically for the expedition supported potential emergency operations by long range helicopters, which were able to reach Polarstern in the event of an emergency at least during the early and late phases of the expedition.