Read our COVID-19 research and news.

Even locked in the ice, the Polarstern produces light, noise, and emissions that could affect many studies.

Shannon Hall

How to erase a ship—Arctic researchers work to eliminate their vessel’s fingerprints

ABOARD THE POLARSTERN IN THE ARCTIC OCEAN—The flare cut through the sky like a firework, sending the polar bears into a panic. They sprinted across the snow, the mom checking to make sure her cub kept pace. Nearby, two polar bear guards—one who had fired the flare and the other armed with a rifle—stood on snowmobiles, making sure the bears posed no threat to the scientists and crew onboard this German icebreaker, which is spending 1 year here in the Arctic, frozen into the sea ice.

The bears are an occasional threat to this unusual expedition, known as the Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC). But the scientists are also contending with another, much larger intruder: their own ship. The 118-meter-long Polarstern is a sophisticated floating lab that allows MOSAiC scientists to study the atmosphere, sea ice, ocean, and life. But the vessel and the equipment it carries also produce noise, light, heat, and other forms of pollution that can ruin measurements in this pristine environment.

The Polarstern's generators, for instance, spew a steady plume of black smoke, complicating efforts to collect air samples. "We are going to be by far the biggest source of aerosol particles in the neighborhood, and that's a problem," says atmospheric scientist Matthew Shupe of the National Oceanic and Atmospheric Administration and the University of Colorado (CU) in Boulder. But, he adds, "It's also an opportunity" to understand how the arrival of more ships might affect the Arctic in the future.

Our encounter with the polar bears occurred just 6 days after the Polarstern locked itself in the ice near 85° north latitude on 4 October. The ship had left Tromsø, Norway, in September, then steamed north in search of an ice floe thick enough to support the scientists and their equipment for the next 12 months, as they drifted past the North Pole before returning to open water between Greenland and Norway's Svalbard archipelago in the fall of 2020. By then, the some 300 scientists involved in the $150 million MOSAiC project, led by the Alfred Wegener Institute (AWI) Helmholtz Centre for Polar and Marine Research in Bremerhaven, Germany, hope to have collected a wealth of data that will help reveal how climate change is affecting the Arctic.

Once the Polarstern's propellers had slowed to a stop, causing the ship to grow still and quiet, the dozens of researchers aboard the first leg of the journey wasted little time in setting up research sites—with names such as "Balloon Town" and "Ocean City"—on the surrounding ice. They graded tracks for roads, raised instrument towers, and strung power lines. (The cables would later become chew toys for the polar bears.) And they used the ship's crane and helicopter to haul heavy equipment onto the icy seascape, including a robotic submarine that the researchers will drop into a hole carved through the 60-centimeter-thick ice.

In some areas, however, they were careful to leave vast fields of untouched snow, where instruments monitor the floe from above and below. Expedition members—including the guards responsible for scaring away bears—were warned not to walk or drive snowmobiles across these sites. It is but one example of the ways MOSAiC scientists are working to minimize the so-called observer effect, in which the very presence of a scientist—or their vessel—can skew their observations.

After helping set up the initial ice camp, 23 participants traveled back home onboard a second icebreaker, the Akademik Federov.


The Polarstern can't be shut down completely, because it must serve as the expedition's power plant, command center, and hotel—which some might call a five-star. There is a dining room that serves mouthwatering cakes every afternoon at tea time, a sauna, a swimming pool, a gym, a bar, and even small shops where you can buy sweets, tobacco, and alcohol. Although the ship is passively drifting with the ice, it will guzzle 15 tons of diesel fuel per day.

Some of that fuel powers the ship's many lights. When I learned that I would be aboard the Polarstern at MOSAiC's start, I looked forward to experiencing the onset of polar night and seeing the North Star—which dangles just 40° above the horizon where I live in Colorado—twinkle close to the top of the sky. But the ship floods the ice with light to enable the researchers to work safely and efficiently, creating a powerful glow that blots out the sky. I did not see a single star during my 2 weeks aboard.

For AWI biologist Allison Fong, the glow is a problem. She wants to better understand how microbial plant life survives in the Arctic winter, when there is no sunlight for months on end, but she can't study samples that have been exposed to artificial light. So, once a week she plans to drive a snowmobile to what she calls the "dark zone" hidden behind a fortress of small ridges of snow and ice some 500 meters from the ship. There, researchers will don red headlamps (red light doesn't affect most organisms) and collect ice cores that they will analyze back at the ship.

Oceanographers, meanwhile, are dealing with the heat, turbulence, and wastewater produced by the Polarstern. "At the main site [around the ship], there's sort of a dead zone" for collecting data, says Tim Stanton, an oceanographer at the Naval Postgraduate School in Monterey, California. To avoid the issue, he and others have deployed a handful of autonomous instruments, which sit on the ice or float in holes, far from the ship.

The expedition's own noises, meanwhile, have forced atmospheric scientists to build special defenses. At a site called "Met City" a half-kilometer from the ship, a barrier nearly as tall as a person shelters an instrument that uses pulses of sound to measure the density of air, and thus gain insight into the structure of the atmosphere. The barrier is designed to deaden any artificial noise that might rumble across the seascape, such as blasts of the ship's horn and the whine of snowmobiles and nearby electronics.

Then there is the Polarstern's sooty exhaust—a huge problem for the many MOSAiC scientists studying the Arctic's unusually clean air. The researchers want to better understand the sources and fates of aerosols—tiny particles suspended in the atmosphere—that contribute to the formation of small ice crystals within clouds. The number of crystals can determine whether a cloud acts as a blanket to warm Earth or an umbrella to shield it from solar radiation. But scientists aren't sure exactly where Arctic aerosols originate: Are they swept north from land, or are they formed by ocean organisms and sent skyward by breaking waves?

Amy Richman, who is producing a planetarium show on the MOSAiC expedition, leans over the edge of a hole cut in the ice at a research station dubbed “Ocean City.”


To gain some insight, Lauriane Quéléver, a chemist at the University of Helsinki, and her colleagues will spend the next year pulling air samples through tubes mounted on a refashioned shipping container that serves as her lab. Instruments will parse the samples, analyzing and counting particles. Quéléver was astonished to find that the number of particles soared to 28,000 per cubic centimeter—a few thousand times greater than the typical Arctic level—when a second icebreaker arrived to swap instruments, personnel, and fuel. "I really hope that I'm going to get some very natural and pristine data," she says. "Otherwise I can just go home."

A snowstorm or strong wind could help her and other scientists by clearing the air, but that rarely happened during my stay. When I visited CU atmospheric scientist Byron Blomquist, he was trying to collect air samples at a tower hanging off the ship's bow. But his instruments weren't sampling anything; they had automatically shut down after an alarm signaled that exhaust from the stern of the ship was enveloping the tower. Inside his container, pumps roared like vacuum cleaners as they pushed clean air out through his instruments, to prevent contamination by the smog.

Yet the Polarstern's soot presents an opportunity for some researchers. As the Arctic warms and sea ice melts, shipping in the region is expected to increase dramatically. Those vessels will likely release black carbon, an aerosol formed by diesel engines. When black carbon settles on snow or ice, it can hasten melting by reflecting less solar radiation and absorbing more heat, a process MOSAiC researchers hope to study in detail by sampling ice close to the ship and a planned aircraft runway.

Less than 24 hours after the Polarstern settled in, the ship's emissions were smudging the ice. I noticed a black flake as large as my fingernail within the icy floe, removed a mitten and picked it up, rubbing the flake between my fingers. It turned to an oily smear.

It wasn't the only preview of what lies ahead. Earlier, I stood on the deck of the Akademik Fedorov, a Russian research vessel that participated in MOSAiC's first few weeks, with Jessie Creamean, an aerosol researcher at Colorado State University in Fort Collins. We watched as the Polarstern slowly approached, gliding across a sea of ice. The sky was gray, with a thin stripe of blue at the horizon in every direction—except at the spot where the Polarstern had just spent the night. There hung a thick yellow and brown cloud. "Just think," Creamean said, "if we open the Arctic to shipping it's all going to look like that."