Warming temperatures are changing the Arctic in unprecedented ways — but for the next 12 months, there will be a regular fixture on the polar horizon.

In an extraordinary expedition that sets off on 20 September, scientists will freeze Germany’s biggest research vessel, Polarstern, into Arctic sea ice, where it will stay trapped for the next year. The ship will host a rotating crew of some 300 scientists from 17 countries and serve as a drifting polar-research laboratory — one that will give researchers their closest ever look at how the polar climate, and its fragile ecosystems, are changing.

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The €140-million (US$154-million) research project, called MOSAiC (Multidisciplinary Drifting Observatory for the Study of Arctic Climate), is one of the biggest research missions ever to go to the Arctic and has been years in the planning. Led by the Alfred Wegener Institute (AWI) for Polar and Marine Research in Bremerhaven, Germany, the expedition commemorates Norwegian polar explorer Fridtjof Nansen’s legendary, but ill-fated, attempt in 1893 to reach the North Pole in a three-masted wooden schooner trapped in drifting sea ice. But unlike Nansen and his men, whose strenuous journey on the Fram lasted three years, the MOSAiC team will rely on a superbly equipped research ship and on logistical support by Russian, Swedish and Chinese icebreakers.

After a first leg in which Polarstern will sail polewards in the open ocean, the vessel will freeze into the sea ice at a latitude of about 85 degrees north, probably in October. The team will then set up a network of camps on the thick ice surrounding the ship. Nearby research stations will be accessible at any time. Those further away — up to 50 kilometres — will be served by helicopters that will transport crew and equipment. Where Polarstern will end up in 12 months’ time is uncertain. Statistical calculations of sea-ice drift suggest possible end points near the North Pole or in the Fram Strait between Greenland and Svalbard (see ‘Uncertain destination’). “We will go and do science wherever the ice might carry us,” says chief scientist Markus Rex, an atmospheric scientist at the AWI.

Arctic unknowns

One major goal of MOSAiC, says Rex, is to improve strikingly uncertain climate projections for the rapidly warming Arctic, and study the effects of climate change on the region’s ocean chemistry and ecosystems.

The Arctic is heating up faster than any other region on Earth. Positive feedback loops, in particular the loss of snow and ice that help to reflect sunlight, have amplified climate change in the region, which has already warmed by 2 ºC over the past century.

Climate models disagree wildly on how much more the Arctic will heat up as the concentration of greenhouse gas in the atmosphere rises and sea ice dwindles. Some models project that the Arctic could warm by about 5 ºC by 2100, relative to the 1986–2005 average, under a high greenhouse-gas-emissions scenario. Others suggest that high northern latitudes might warm by more than 10 ºC. The region has already changed dramatically: the extent of sea ice in summer has halved since the 1970s, and the ocean around Norway’s Svalbard archipelago has been largely ice-free even in winter in some recent years. Winter air temperatures there have been more than 7 ºC higher than normal in recent decades.

“The Arctic has changed very much since the days when Nansen was here,” says Rex. “If climate change proceeds unabated, it will turn into a completely different environment.”

Data deluge

Scientists worldwide are eagerly awaiting the wealth of data that the MOSAiC team hopes to collect. “This is a truly wonderful opportunity for the entire climate and polar-research community,” says Jens Hesselbjerg Christensen, a climate scientist at the University of Copenhagen.

Among the data will be continuous measurements of the heat exchanged between the atmosphere and the Arctic surface over the four seasons. This information will help scientists to understand why the region is warming at least twice as fast as the rest of the globe, says Mark Serreze, director of the National Snow and Ice Data Center at the University of Colorado Boulder. Current climate models don’t seem to correctly capture energy fluxes and sea-ice change in the Arctic, he says. The models are also poor at representing changes in cloud cover and cloud properties, which have a substantial effect on the Arctic climate, he notes. “We don’t know nearly enough about clouds, we just haven’t got the data. MOSAiC will hopefully provide just that.”

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Changes happening in the Arctic have enormous environmental implications far beyond the region, says Serreze. Thawing permafrost, for example, threatens to release large amounts of carbon locked in frozen soils.

And the Arctic is linked with the atmosphere and the climate at lower latitudes. Some scientists suspect that Arctic warming is altering the meandering high-altitude air currents — known as jet streams — that drive the weather across the entire Northern Hemisphere. But the amplification of Arctic warming might also be the result of changes in global atmospheric circulation, rather than the cause. Data from MOSAiC, when plugged into climate models, should help to clear that up, says Serreze.

MOSAiC crew members training on ice in Finland in February in preparation for the expedition.Credit: Alfred-Wegener-Institut/Roland Kerstein

Ice explorers

A number of Serreze’s colleagues from the University of Colorado will be on Polarstern, along with scientists from countries including China, Russia and Japan. Participants will each spend about 10 weeks on the ship. Scientists, food and supplies will be ferried to and from the vessel by one of four icebreakers.

Life and work under extreme Arctic conditions is a special experience, physically and emotionally, says Rex, who plans to spend 10 months on board. From late October to the beginning of March, the teams will be in the dark polar night. There are risks: participants must pass a medical exam before being granted a berth on Polarstern, and all are given rifle and polar-bear training. At least six people will be on polar-bear watch at all times to ensure that researchers are safe while working the ice. But there is time to relax, too. Once a week, scientists are free to grab a drink or two in the Zillertal, the ship’s bar.

Most of the science will be done by young researchers. “I never expected that I would take part in something so exciting,” says Elise Droste, a PhD student at the University of East Anglia in Norwich, UK, who studies how sea ice affects carbon uptake by the polar ocean. “This will be a tremendous experience — slightly nerve-racking but monstrously beautiful.”