MOSAiC follows the same idea Fridtjof Nansen had 127 years ago: letting nature itself be the navigator to cross the North Pole. Nature alone will dictate the research vessel Po- larstern’s course, allowing a total of several hundred researchers on board during different phases of the expedition to experience the Arctic winter close up. Arctic sea ice mainly forms off the coast of Siberia – the region considered by some as the birthplace of the Arctic ice masses. From there, the ice drifts slowly across the Central Arctic, and, after a year, is carried southwards via the Fram Strait east of Greenland to the Atlantic, where it eventually melts. This phenomenon is known as Transpolar Drift. However, not all Siberian ice heads directly toward the Fram Strait; some of it takes a route north of Canada and Alaska and becomes trapped in the so-called Beaufort Gyre, where it may remain for several years. During this time, the ice develops into enormous ice floes. In September 2019, when the sea ice is at its thinnest, the “Polarstern” set sail to the Siberian coast to become locked in the ice. To this end, the ship has been moored to an older ice floe that is thick enough and several kilometres wide, offering enough space for an aircraft landing strip as well as the central research camp. The Polarstern's yearlong drift through the Arctic Ocean has begun.
Polarstern left Tromso on 20 September 2019 and headed to 85° N, 135° E where, after a few days of searching by Polarstern and the support vessel Akademik Fedorov, the MOSAiC team found a suitable ice floe (at 85° N, 137° E).
In a race against the approaching darkness of the polar night, the research and measuring stations were set up and deployed before 9 October. Around Polarstern, the so-called Ice Camp was set up on the ice floe, including a sophisticated infrastructure and the various "city parts" of the science teams. Meanwhile, the international team on Akademik Fedorov deployed the complex network of buoys and measuring stations up to 40 km away - called the Distributed Network. This network will also drift around the central observatory Polarstern. At the end of October, Akademik Fedorov left Polarstern - and the isolated drift of Polarstern began.
Around mid-December, the first support vessel reached Polarstern: the Russian icebreaker Kapitan Dranitsyn. Not only did this ship bring fuel and supplies to Polarstern, but also the next science team and the crew that will now cover the second leg of the MOSAiC expedition – the leg entirely taking place in the polar night.
This exchange of personnel, food and fuel will be taking place under the most challenging ice conditions. Once again, the Russian icebreaker Kapitan Dranitsyn will be working her way through the massive ice of the Arctic winter to Polarstern. Even if the ice conditions do not allow Kapitan Dranitsyn to reach Polarstern, the fuel supplies on board Polarstern would suffice to provide the ship with heating and electricity until the next refueling in mid-June.
At this time, the Arctic sea ice is too thick even for icebreakers - but at the same time it is thick enough to operate an aircraft runway on the ice. The exchange between leg 3 and 4 will therefore rely on aircraft. With the help of Antonov aircraft, the approximately 100 people on Polarstern will be replaced. A resupply routine, however, will be omitted at this point.The flights start in Longyearbyen on Spitsbergen. There are alternative plans for this exchange as well: If the ice turns out to be too thin for a runway, the personnel rotation will be carried out with the help of long-distance helicopters taking off from Cape Baranova.
The next refueling operation in the Arctic summer is carried out with the help of the Swedish icebreaker Oden. Since refueling is not possible in April, Polarstern will also need fuel for helicopters and airplanes at this point. The crew and scientists will also be replaced and new food and equipment will be supplied.
With the support of the new Chinese icebreaker Xue Long II (Snow Dragon), the last big refueling and personnel rotation is carried out before the start of the last leg of the expedition. Once again, the supply vessel brings the next scientific team and a new crew to the drifting Polarstern - as well as food, equipment and fuel.
Depending on the ice situation, Polarstern will continue its research in the Arctic until September 2020. Towards the end of September, the drift is expected to be completed and the ship will have reached an end point in Fram Strait. Polarstern will then free herself from the Arctic ice and embark on her journey home. As far as possible, some instruments from the Distributed Network will be collected and taken home. After a detour to the Kongsfjord (Spitsbergen) for further research, Polarstern is scheduled to return to Bremerhaven (Germany) on 12 October 2020.