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SNAPSHOT A drift in the

The central Arctic is a challenging location to reach and to study but plays an important role in the . Covered in sea year-round, with midnight sun in the summer and polar night in the winter, it hosts a unique marine and sea-ice ecosystem. By no means is it a static environment; the ice is constantly shifted by the ocean and the winds, creating a unique landscape. Understanding the Arctic requires observations in the field, as remote sensing is limited, and many processes take place on a smaller scale than can be detected remotely. This is why the German RV Polarstern is set to spend a year locked in the ice, collecting Credit: Alfred-Wegener-Institut/Mario Hoppmann measurements that will unravel the key climate processes that take place there. The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) has a robust basis for modelling of the Arctic, collected data back to institutes, allowing just set sail from Tromsø, Norway. But this [to ultimately provide] improved and more further analysis to that started onboard. is not the first drift expedition in the Arctic. reliable global climate models,” says Rex. Many things have changed in the 126 In 1893, a specially strengthened The RV Polarstern with her 101 years since Nansen set off — climate wooden vessel, the , led by Fridtjof personnel of researchers, logistics support change is altering the Arctic. But many Nansen, with Otto Sverdrup as captain, and crew will enter the ice in the Siberian of the challenges of polar exploration set off aiming to reach the geographic Arctic, around 130–140° E, with the remain with unpredictability of the hostile North Pole. The ship entered the ice in expectation that by 85° N they will be environment. When the Norwegian Polar the east Arctic, and the explorers firmly sufficiently into the ice pack to switch off Institute tried a shorter drift experiment locked their vessel in the pack ice to the engines and allow the Arctic to decide as a precursor of MOSAiC, mostly in the harness the theorized Arctic east–west their course for the next year. “The start marginal ice zone north of Svalbard, in current. Although they were not successful point is the only degree of freedom,” says 2015 onboard the RV Lance, the ship was in reaching the pole, the ship survived Rex, so it has been planned carefully to moored to a large floe, but storms and 3 years in the ice and proved that the give the best chance that the ship remains wind pushed the ship out of the ice pack east–west drift could transport a vessel in the ice for the intended 350 days. Once after only 5 weeks locked in. The team across the Arctic. in the desired position, the expedition will re-entered the ice and ended up spending The premise of MOSAiC was sparked identify a large floe, sufficient to support 111 days overall in the ice pack but needed in 2010 by an idea put forward by Klaus the desired experimental work, and moor to tether to different floes through that Dethloff of the Alfred Wagner Institute themselves to it. time as the conditions altered the plans. (AWI) in Potsdam, Germany. Markus Rex, Mooring to a large ice floe creates The remoteness will offer challenges to head of MOSAiC and expedition leader, a floating laboratory platform, with the 600 participants over the year, but the recalls that it seemed “too challenging equipment set up on the ice to take opportunity that MOSAiC offers is vast, logistically but the idea did not go away.” measurements, and scientists collecting a with many first-time measurements that The idea grew, and funding from AWI variety of observations — ocean, ice and could lead to exciting breakthrough science. pushed it into reality. Seventeen nations atmosphere — during the Arctic crossing. Although there will not be great connection are now involved in the project, which About a third of the research during with the outside world, daily updates will study a wide range of questions: the MOSAiC will be ship-based, and two- will be posted on the web app (https:// surface energy budget, from the small- thirds will be conducted on the ice. follow.mosaic-expedition.org) as well as scale atmospheric eddies some 10–20 m The ship will be supported by four updates on Twitter (@MOSAiCArctic) across to radiative fluxes; the properties of as well as aircraft for resupply and Instagram (@mosaic_expedition), and aerosols; and its changes and personnel changes, which will happen including ‘picture of the day’. ❐ across the seasons; the ocean’s physical every 2–3 months when possible. Aircraft properties; ecosystem functioning through will be used when the ice thickness Bronwyn Wake the midnight sun and its all-day light, prevents ship resupply, and this will and the opposing polar night; along with require construction of a runway on the Published online: 25 September 2019 many more. The project aims to “provide ice. Resupply will also aid the transfer of https://doi.org/10.1038/s41558-019-0597-3

Nature Climate Change | VOL 9 | OCTOBER 2019 | 729–733 | www.nature.com/natureclimatechange 733