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The icebreaker Polarstern, seen here operating in Antarctica in 2013, is being prepared to be locked into Arctic sea ice for more than a year.

Alfred Wegener InstitutE/Stefan Hendricks

Arctic researchers will lock this ship in ice for a year to study the changing polar region

In 1893, Arctic explorer Fridtjof Nansen of Norway deliberately froze his wooden ship, the Fram, into the drifting sea ice north of Siberia. His rationale: Rather than fighting the ice, which had thwarted previous efforts to reach the North Pole, he’d allow the ice itself to carry him close to his goal. His polar bid failed, but 3 years later the wandering pack had carried the Fram some 2000 kilometers across the Arctic to the open North Atlantic Ocean, making Nansen an international hero. His mission revealed fundamental facts about the mysterious Arctic Ocean, including its depth, the enormity of its pack ice, and the currents that move heat, water, and ice across the top of the world.

Next month, an international expedition led by the German icebreaker Polarstern will pay homage to Nansen’s strategy in the biggest Arctic science expedition to date. The ship will depart Tromsø, Norway, in late September, then let itself become trapped in the ice. Researchers plan to spend the next 13 months drifting past the North Pole before returning to Germany in the fall of 2020.

During the voyage, some 600 scientists from 17 countries will conduct studies as part of the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC), which will also involve a host of aircraft and other icebreakers. Eight years in the making, the $134 million MOSAiC will monitor the rapidly changing Arctic’s physical, geochemical, and biological systems, from the start of sea-ice growth in the fall through its breakup the following summer. “For an Arctic marine biologist this expedition is a dream come true,” says Rolf Gradinger, of the Arctic University of Norway in Tromsø.

Were Nansen alive today he wouldn’t recognize the Arctic. MOSAiC’s focus will be the startling changes that have occurred in just the past 4 decades, and their implications. Summer sea ice now covers half the area it did in 1985, and the Arctic has lost a whopping 75% of its ice by volume. Thick ice packs built up over several years of freezing have been mostly replaced by thinner ice formed over a single winter. As a result, “Much of our accumulated knowledge on an Arctic system dominated by multiyear ice may not be relevant,” notes the MOSAiC science plan. Existing climate models, for instance, do a poor job of forecasting how fast the thinner ice dwindles in warm summers or where it moves.

After their planned 20 September departure, MOSAiC leaders will face a crucial early decision: where to freeze the ship, which will determine its drift track over the next year. They’ll use oceanographic models and previous experience to try to position themselves within a current where the sea ice is mostly young—first-year ice is the preference—but also stable enough to allow researchers to leave the ship and work on the frozen surface.

Adjacent to the ship, scientists will track the evolving ice and the waters below it in fine detail, with buoys along with instruments in and below the surface. Overhead, a phalanx of sensors, aircraft, and balloons will probe the Arctic atmosphere, which has warmed twice as fast as the planetary average. They’ll also use snowmobiles and helicopters to establish a network of autonomous stations on the ice at a radius of up to 50 kilometers from the ship. That size corresponds to the resolution of key climate models, so the stations will provide measurements at a finer scale.

Space-based sensors already collect some of those data. MOSAiC scientists will ground truth the remote-sensing data from satellites and measure things satellites can’t see, such as phenomena under the ice. For example, remote observations have suggested that ice loss, by allowing more sunshine to reach the water, has increased the growth of marine plants called phytoplankton. But that idea “is based on remote sensing [only] during the ice-free period. And we don’t have such observations from the central Arctic,” says Gradinger, a leader of the expedition’s ecosystem team. MOSAiC aims to help fill such gaps by documenting solar radiation levels, plankton populations, geochemistry, clouds, and other factors. Scientists say the data will help them improve their forecasts of Arctic change.

Researchers hope the long, close encounter with the ice will also help them understand small-scale processes that may have an outsize impact, such as the growth of melt pools that darken the ice and absorb heat, hastening the melt. Springtime flights by MOSAiC helicopters, planes, and drones will provide week-by-week detail as the pools grow—critical input for simulations of melting that Ryleigh Moore, a Ph.D. student in applied mathematics, is developing at the University of Utah in Salt Lake City. Being able to see “melt pond evolution over an entire spring season will really open up my research,” says Moore, who will work aboard the Russian research vessel Akademik Fedorov. It is one of four icebreakers that will resupply the Polarstern and rotate scientists in and out, with most stints lasting up to 3 months.

Led by the Alfred Wegener Institute (AWI) Helmholtz Centre for Polar and Marine Research in Bremerhaven, Germany, MOSAiC faces major logistical challenges. Locked in the ice, the Polarstern won’t be able to dodge storms. In case aircraft are needed to respond to medical or other emergencies, the crew will build an ice runway near the ship and tap aviation fuel supplies the mission will stash on Russian islands. To guard against polar bears, the expedition will rely on constantly scanning thermal cameras, a tripwire, and a patrol armed with rifles.

The hardest challenges for researchers aboard the crowded ship, however, may be psychological. It will be “a pretty demanding, high-stress environment,” says Gradinger, whose team of eight biologists has “an exceptionally dense program” of sampling to execute. MOSAiC scientists expect that Polarstern’s sauna, swimming pool, and two bars will provide crucial camaraderie. (In contrast to many polar vessels, alcohol is allowed on the ship.)

“We’ll look out for one another,” says expedition leader Markus Rex of AWI. But he expects the extended time away from loved ones will be “one of the biggest hardships.” He will be apart from his wife and sons, 9 and 11, for 10 months—the longest separation of his career. But the boys “are so excited about” their dad’s expedition, Rex says, and “that makes it a little easier to accept.”