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In January 2012 Jorgen Berge and two colleagues were tooling around Kongsfjorden, on the coast of Svalbard, in a small rubber boat with an outboard motor. The fjord, a stopover site on a two-week-long sea-ice research cruise, provided a rare opportunity to look for marine life in shallow, open waters in the high north during the dead of winter. It was the middle of the night, but the hour didn’t really matter: In the Arctic at that time of year, darkness coats everything, day and night. As does a bitter cold, so the three Norwegian scientists had donned heavily insulated, traffic-cone-orange suits accented with reflective strips—helpful should anyone tumble into the icy water and require rescue. As the team motored along, an eerie glow began to surround them. Berge, mesmerized, leaned over the gunwale for a closer look.

“There was this fantastic spectacle of blue-green light in the water,” he says via video chat on Skype. Berge, an amiable marine biologist whose face is framed by a neat reddish beard, is gesticulating as he describes the pool of , tiny organisms that are the foundation of the marine food web. In his fervor, he seems at risk of knocking over his red wine and frying his laptop. “I felt like lightning had struck twice,” he says.

That’s because two years earlier, in January 2010 in the same fjord, Berge’s team had documented bioluminescent zooplankton, and gone on to of such a sighting in the Arctic. On that trip, they also spotted five seabird species never recorded overwintering in the area, which at 79 degrees latitude is more than 12 degrees north of the Arctic Circle. In 2012, when Berge came upon the glowing organisms again and sensed the shadowy avian figures flying around in the darkness, he resolved to catalog this little-known world. “It was basically just assumed that nothing happened in the Arctic during the polar night, that it was a time of resting,” says Berge. “But what we were seeing told a different story.”

Over the next three Januarys, he and 100 scientists and grad students from seven countries discovered that instead of shutting down when the lights go off, or leaving the area entirely, animals in this fjord bustle throughout the endless black—feeding, growing, and even reproducing. As the Earth hurtles toward an ice-free Arctic, something the region hasn’t experienced , the group’s work, published in the October 2015 issue of , may offer a glimpse of the future. “We couldn’t have done this study 10 years ago,” says Berge. “Back then sea ice a meter and a half thick covered the fjord.”

“It really is quite a significant study,” echoes Tony Gaston, who has researched seabirds in the Canadian Arctic for decades and wasn’t involved with the project. Gaston and others had suspected that warming would open up new habitats for some seabirds in winter; for them to survive, the lower levels of the food chain would have to keep ticking. “We’re now finding that birds are staying much farther north than expected, especially in the Barents Sea. There’s so much more open water up there now.”

Berge’s is just one endeavor shedding light on the mysteries of the Arctic polar night and documenting the dramatic shifts climate change is causing. Sensors are detecting larger, near shore—some nearly two stories high—as sea ice shrinks. Satellite tracking has found that no longer winter in Greenland but on pack ice in the Davis Strait, off the island’s west coast, where they’re thought to scavenge scraps left by polar bears—an increasingly tenuous survival mechanism, given that the latter’s numbers are expected to plummet 30 percent by 2050, to . And underwater microphones deployed off Alaska have revealed that summer whales are hanging around into winter, months later than usual, likely due to the growing expanses of open water. (Eavesdroppers got a shock when they —a behavior thought to be confined to the whales’ tropical breeding grounds.) The polar thaw is also providing access to previously inaccessible reaches, offering unprecedented opportunities for development, shipping, fishing, and scientific expeditions to places like Kongsfjorden.

Each January the polar explorers for two weeks. (“I know you probably want to hear how difficult the living conditions were, but it was no hardship at all,” Berge says of their research facility, which had hot showers, good food, a pool table, and a stocked bar.) With so many scientists vying for time on the research vessel and small boats, they worked around the clock to squeeze in all the fieldwork, enduring fierce winds and temperatures that dipped to minus 40 degrees Fahrenheit. Berge estimates that in half a month they would pack in the equivalent of 900 researcher days in the field.

From the sunless dawn through the wee hours, they deployed baited traps and time-lapse cameras to capture an abundant, busy community of crabs, whelks, and other shallow-water scavengers. They found thriving kelp forests, and in the water column measured respiration rates higher than those recorded in summer. They watched as filter-feeding Icelandic scallops kept right on growing during winter, likely consuming the debris, called “,” floating around them (their usual food source, phytoplankton, was present only in low numbers). Polar cod and herring, prey for many seabirds, foraged in the frigid waters. Copepods, krill, and other zooplankton were actively reproducing, and keeping more or less to a circadian rhythm, surfacing during the night to feed and sinking into deeper waters during the invisible shift to daytime hours—supporting recent research indicating that Arctic organisms detect light levels the human eye can’t.

When the wind would die down, and as the temperature inevitably plummeted, Berge would bundle up and head out in a Zodiac in search of seabirds, his eyes slowly adjusting to the darkness, which was occasionally offset by the moon, the stars, or the dancing green and red glow of the northern lights. “It’s almost magical when you’re out there,” he says. “Your system is on full alert, and you’re more aware of your surroundings.”

Those outings familiarized Berge, a plankton expert, with the birds’ quirks: the way Northern Fulmars would circle tantalizingly close overhead but never land on the water, or how the crew’s headlamps attracted Black Guillemots. He grew especially fond of Dovekies, which would surface, chatter briefly while they regrouped (“as if making a plan,” he says), then disappear into the dark water. Berge’s team saw hundreds of birds from six species, and collected five Dovekies, three Thick-billed Murres, one Black Guillemot, one Northern Fulmar, and one Glaucous Gull (the Black-legged Kittiwakes eluded them); the specimens they collected were all healthy, and many had stomachs packed with fish, crustaceans, or zooplankton.

While some seabirds, like Black Guillemots, are known to overwinter in the Arctic, the findings surprised Nina Karnovsky, an ornithologist at Pomona College who studies Dovekies in Svalbard during the breeding season. “The fact that there were Dovekies hanging around in winter totally blew me away,” she says, explaining that the small planktivores have high metabolisms and therefore need a lot of food to survive, especially when the mercury drops.

It’s possible that some birds have always stuck around with nobody noticing, but a more likely explanation is that Berge’s team has documented a new phenomenon brought about by the disappearance of sea ice. “I think what we’re seeing is a sign that warming is leading to changes in behavior of Arctic birds,” Karnovsky says. “It underscores that we really need to understand seabirds’ entire lifespans—not just when they’re at breeding colonies—to understand how climate change is affecting them.”

While the vast majority of seabirds that breed in Svalbard continue to migrate, there may be benefits for those that can hack the winter at higher latitudes. Those that stay might get first dibs on next year’s nesting sites or face less competition for food. But whether those food sources remain plentiful in the fast-changing Arctic, or even become more abundant—or, indeed, scarcer as ocean acidification and sea surface temperatures increase—remains to be seen. 

Mark Mallory, a member of the in Canada and lead scientist on the Ivory Gull satellite tracking project, says the study also raises intriguing questions about bird senses: “How the hell are these birds zooming in on the food they want in the dark?

“I’d always assumed that birds staying at really high latitudes fatten up in fall as much as they can, then live off those reserves until enough light appears for them to forage again,” he continues. “It’s pretty bloody shocking that they found fat birds with full bellies.”

And yet it’s not entirely surprising that several of these species might make a go of it in the dark. At 33 feet below the surface, the ocean has typically absorbed the vast majority of visible light, but Dovekies, Thick-billed Murres, and Black Guillemots are known to dive more than 100 feet deep, which tells us they must have some ability to forage under low-light conditions. Northern Fulmars, meanwhile, have a keen sense of smell, which would come in handy when feeding in lightless conditions.

Still, those characteristics don’t explain precisely how the birds locate dinner. Bioluminescent plankton would seem to be an obvious beacon; both the Dovekies and murres Berge collected had recently dined on a bioluminescent krill species, Thysanoessa, and fish-eating birds could home in on prey that was dining on those glowing morsels. But birds were also foraging when the light show was absent. Seabird biologists interviewed for this story had numerous, in some cases highly speculative, hypotheses. Perhaps the birds’ eyes are far more sensitive than we know, enabling them to use starlight or low levels of solar light that we can’t detect. Or maybe they’re feeding only at shallow depths, where they can see prey. Or—and this is where it gets wacky—they could have other senses that we know nothing about: feathers or other organs that act like antennae and pick up turbulence left by a moving object, say, or bat-like capabilities that allow them to ping their way to prey. For now it remains a mystery. 

This January Berge’s fieldwork in the Arctic will be a quieter affair. He’ll deploy a variety of instruments that measure acoustics, light, and the physical properties of the icy waters, and also squeeze in some work on the bioluminescent zooplankton that fascinate him.

He hasn’t lost the bug for winter cataloging binges, however. He’s hoping that this time next year he’ll be leading an expedition into the open waters off northern Canada. After all, he says, we now have a snapshot of winter in one spot, but little idea if other open-water areas across the vast region see similar activity.

“It’s critical to deepen our understanding of the Arctic right now,” says Mallory. We are unwittingly rewriting the rules for survival at the top of the world, forcing wildlife there to adapt faster than ever before. At the same time, we have an immense opportunity, given the current hiatus—likely temporary—in oil and gas development, and the lull before fishing and shipping explode across the region, to monitor the far-flung locales and species in ways never before possible.

Those efforts will be key to identifying and safeguarding the region’s most biologically important areas. And they could reveal marvels beyond even bioluminescence and unexpected winter inhabitants. Surely the Arctic hasn’t given up all of its secrets yet.