In an Increasingly Noisy Arctic, Will Narwhals Fall Silent?

Late one August evening three summers ago in Fønfjord, a fifty-mile-long channel in Scoresby Sound, East Greenland, two narwhals were netted by local hunters and towed into the shallow waters off Hjørnedal, a small field station. The Arctic night a thousand or so miles from the North Pole is not entirely dark in late summer, but the Hjørnedal team—Inuit narwhal hunters collaborating with a group of researchers—needed headlamps. As quickly as they could, they untangled the narwhals and fitted each with a heart-rate monitor, a satellite transmitter, and a listening device called an Acousonde. The misshapen right pectoral fin and scars on the mottled many-shades-of-gray skin of one narwhal looked familiar. The team recognized Nemo, a young male with a modest thirty-two-inch tusk, first caught in 2014.

Within thirty minutes of capture, the abundantly instrumented Nemo swam back toward Fønfjord. He dived a few times, presumably to the bottom of the Hjørnedal bay, where he dislodged the suction cups that fastened the heart-rate recorder to his back, a maneuver he had perfected four years earlier. He swam north into Rødefjord—a thirty-mile-long fjord as broad as a small sea and, in August, traversed by thousands of icebergs, many echoing the shapes of the mountains where they originated.

For hours, Nemo didn’t make a sound, as is true of most narwhals after catch and release. He never went much below three hundred and twenty feet (narwhal travelling depth) until, at three o’clock in the morning, he dived eight hundred and twenty feet or so (nearing narwhal feeding depth) and clicked. Narwhals can make as many as a thousand clicks every second, and emit them in a wide or narrow beam of sound that returns an aural portrait of shapes and distances at some of the highest resolutions known for animals. Such resolution is vital in winter darkness and dense pack ice, where cracks or holes, portals to air, open in less than three per cent of the frozen sea. Nemo dived to two thousand feet, where there is no light, the water is on the cusp of freezing, and there is prey, likely squid, halibut, capelin, and polar cod. Nemo’s clicks and buzzes indicated that he was hunting. Soon after, he made his signature call: a short series of clicks, also called a burst pulse, followed by a high-pitched whistle, repeated in sequence. (Each narwhal has its own particular vocalization, and, although the calls are thought to be social, their exact role is unclear.)

Life for Nemo was back to narwhal normal—calling and hunting and eating—until a little after six the following morning, when he heard sounds that were not the familiar rush of submarine currents from melting glaciers, the wind making waves, the earthquake-like rumble of calving ice sheets, the loud report of an iceberg cracking, nor the thunder of one flipping. Rounding the tip of Milne Land, the largest island in Scoresby Sound, was the Royal Danish Navy vessel Lauge Koch. On board was the seafaring half of the Hjørnedal research team. They were making a racket, on purpose. In addition to incidental noise from the engine and the pinging of the ship’s side-scan sonar, a seismic air gun issued a loud underwater blast—producing a sound like a detonation—every eighty seconds.

Nemo stopped buzzing. He swam toward the surface, where he could breathe as often as he liked, and he raced away. The water rushed past the Acousonde, the listening device still fastened to his back by suction cups and a magnesium coupler that slowly dissolves in salt water. “He is swimming so fast, he is stroking so fast, I cannot hear anything,” Susanna Blackwell, a marine-mammal-acoustics expert with Greeneridge Sciences who was aboard the Lauge Koch, said. “He is Mr. Freak Out.” For roughly twenty-four hours after hearing the ship and the air gun, Nemo did not vocalize or, perhaps critically, hunt or eat. An experiment with a single, comparatively small air gun—less powerful than those often used simultaneously with dozens of others during oil-and-gas exploration—had stressed out one of the Arctic’s most elusive creatures.

Much of the marine world has become loud like a perpetually congested highway, thick with motors and horns and sirens. Comparatively, the Arctic has been like the countryside, as Blackwell, the acoustic lead on the Hjørnedal team, told me—with the occasional lawnmower or leaf blower. By and large, she said, the region “has been protected from industrial noise in a way that no other place on the planet has been.” But, as sea ice rapidly diminishes in extent and duration, the Arctic is losing its sound-attenuating cover of ice, and vessel traffic is increasing as shipping routes open and resource exploration amps up. “For many reasons, the problems are compounded in the Arctic, because it has been so isolated for so long,” Blackwell said.

The problems are extensive. In the past fifty years, the oceans have become vastly noisier as a result of, among other things, boat and ship engines (there are some ninety thousand merchant vessels alone), seismic surveys for fossil fuels, military sonar, and blasting for mining and for oil-rig and wind-farm construction. Comparisons between sound levels in water and in air are challenging, as are comparisons between what animals hear and how people would experience something similar. Even so, a container ship to a whale may sound like a speaker-proximal seat at a rock concert—and though the fan has chosen to be that close to the clamor, the whale has not. Noise can travel in water more than four times faster than it does in air, and can reach for hundreds and sometimes a few thousand miles, depending on the source and frequency of the sound and the qualities of the water column—namely its temperature and salinity.

Much of the increase is in low-frequency noise, the frequency band that many marine mammals, baleen whales in particular, use to find mates and their offspring, to hunt, and to share information. “That is a very worrisome trend, of course, because that means that these long-distance communicators can’t hear each other any longer,” Blackwell said. She has spent a decade studying bowhead whales in the Beaufort Sea, part of the Arctic Ocean north of Alaska, and estimated that she has analyzed several million bowhead calls. At low doses of air-gun sound, the bowheads called more often, perhaps trying to insure that their messages were heard. When the source of noise was closer and the air-gun pulses were louder, the whales stopped calling. At some point, Blackwell and her colleagues concluded, the whales may have found that calling—to communicate about location or food, to find mates or calves—was no longer worth the effort, because it had become too difficult to decipher the information in the call.

In addition to disrupting communication, background and short-term noise have been linked in whales to stress responses (which can impair immune-system and reproductive health), to fatal strandings, and to population declines. More than a hundred studies have also documented adverse effects on cephalopods, fish, and other organisms. In 2018, Lindy Weilgart, a marine-noise-pollution expert at Dalhousie University and OceanCare, a conservation organization, did a review of all related studies. She found that noise appears to be disruptive to nearly every creature studied so far. In fish, it can impair reproduction and disrupt schooling and other important behaviors, such as avoiding predators. Loud noise can flat out kill zooplankton, tiny creatures that help support the global marine-food web.

But how narwhals respond to the cacophony attending human marine activity has been unknown. Assessing those impacts for the northernmost-ranging cetacean is important to formulating shipping, mining, and seismic guidelines and regulations as the region becomes a thoroughfare. By the most recent estimate, around a hundred thousand narwhals currently exist, most of them in Canada and Greenland. In the nineties, regulators approached some expert Arctic biologists for guidance. “We were being asked to come up with advice on how to avoid disturbing the marine animals,” Mads Peter Heide-Jørgensen, a professor at the Greenland Institute of Natural Resources and the University of Copenhagen, and the leader of the Hjørnedal team, said. Because Scoresby Sound, on Greenland’s least populated coast, had experienced scant human noise, it seemed an ideal place to study anthropogenic acoustic impacts on narwhals. “A good little aquarium, so to speak, where we were under controlled conditions,” Heide-Jørgensen said.

For the first six years, the Scoresby Sound team studied the narwhals’ acoustic world from shore. Hunters were paid about five thousand dollars for each netted live whale. In 2017, with funding from various government agencies, including Greenland’s Mineral Resources Authority, Heide-Jørgensen hired a research vessel to blast a small air gun to assess the narwhals’ response. Without such demonstrated cause and effect, the impact of air-gun noise would remain speculative. “It is fair to say that this is one of the few studies where we have some control over both sides: exposure and a measure of the reaction,” Blackwell said. In the summer of 2018, the team repeated the experiments with a larger gun—albeit still small by industry standards.

Nemo’s Acousonde stayed on from August 24th until August 29th, and ultimately dropped off near the four-mile-wide terminus of Syd Brae, or South Glacier. One of the team’s findings has been that narwhals spend a lot of time where glaciers meet the sea; minerals scraped from land likely make those phase boundaries rich hunting grounds. Nemo’s recording device floated to the surface, a yellow-and-red speck in a massive fjord system, broadcasting its presence with an ultra-high-frequency transmitter.

During the six days that Nemo was collecting samples of his acoustic life, the Lauge Koch had commuted hundreds of miles up and down and in and out of fjords, releasing floating hydrophones that could capture background decibel levels for the air gun and reveal how noise moved through the fjord system—data that could help interpret recordings from the narwhals themselves. Blackwell spent a lot of time conferring with the leader of the seismic team, Per Trinhammer of Aarhus University, in Denmark, about where and how deep to hang the hydrophones. At one point, she devised a configuration—an elegant, conjoined array of hydrophones hanging at different depths from triads of yellow floats—that she was pleased with. “It is important that your science be beautiful,” Blackwell told me, as she worked on the setup, “although you get more respect when it looks like a mess, because people think you are a genius for cobbling things together.”

As the hydrophone fact-checking arrays were designed, debated, and deployed, the ship followed ever-shifting directions from Hjørnedal about where to find tagged narwhals or instruments that had fallen off and needed to be picked up. Every fjord began to look familiar: Øfjord, Rypefjord, Harefjord, Vestfjord, Rødefjord, Fønfjord, Gåsefjord. The brae, or glaciers, too. Not the icebergs, though, which shape-shifted and morphed as they voyaged. Just as cloud watching invites imaginings, so, too, does iceberg watching: one is a Cubist bull, one an origami crane, another Totoro, a truffula tree, a manatee, a mermaid, a swan, a bear, a castle, a mountain, a metropolis.

By late evening on August 29th, the Lauge Koch was close to Syd Brae, homing in on the signal from Nemo’s Acousonde, and also one from Siggi, the narwhal caught with Nemo. The great gray warship was to the recording device as a barn of hay is to a needle. Three crew members went out in a rigid-hull inflatable boat (RIB), scanning the black water under an ivory moon, skirting icebergs, listening for the beat of the Acousondes. The bridge hushed as the pilot wove a path through water dense with icebergs and their smaller relatives, bergy bits and growlers. People peered into the charcoal-gray night trying to keep the boat in sight and to spot a yellow-red pinprick. The temperature dropped. The search was called off.

In the morning, some crew members manned the walkways on either side of the bridge, watching for underwater bergs. In the tremendous and often treacherous East Greenland landscape, even a warship becomes a fragile miniature. It took two hours, but the RIB brought back both Acousondes. Blackwell wrapped them gently in plastic—one of her colleagues at Greeneridge Sciences, William Burgess, invented the instrument and continues to make some of the parts by hand. Then she settled into her makeshift office, the Lauge Koch’s hazard-exposure-decontamination room, to look at the data. Nemo’s device contained two hundred and thirty-five sound files—more than a hundred and ten hours of recordings. “It’s nothing to scoff at,” Blackwell said.

Some narwhal-sound analysis can be done with software, but much of it needs a human ear. “I find it absolutely fascinating to be part of their life, to hear what they hear,” Blackwell said. “It is like, when you listen to a piece of music over and over again, you hear more things, more layers.” It was Blackwell who suggested naming the Scoresby Sound whales instead of using scientific convention or instrument numbers, in which Nemo would be 027 or 20160 or 7926 or B4. “It is so much easier to say Freya than B25,” she said, noting that Frans de Waal, a primatologist at Emory University and a well-known author, shaped her approach to animals.

Findings from the two summers of sound studies are just starting to be published. It appears that Nemo’s stressed-out response was part of a pattern. Air-gun blasts and proximity to the ship caused narwhals to stop echolocating—that is, they stopped hunting and feeding. Social calling sometimes increased and at other times stopped, meaning that that their communication was disrupted in various ways. Some narwhals raced toward shallow shore water. The air gun, detonating generally once every eighty seconds, could be heard by the whales as far away as twenty kilometers or more in some instances, and the sound could bend around islands. Such sound attenuates quickly close to the source, “but, once it gets just above background, it can take forever for a sound to no longer be audible,” Blackwell said. “And, if you are an animal that hearing something is enough to make you upset about it, well, that is going to be problematic.” The side-scan sonar, which is higher frequency, louder, and pings fifty-six times in eighty seconds, didn’t travel far in Scoresby Sound. “It may be very powerful at short distances, but the whales can’t hear it at long distances,” Heide-Jørgensen said.

The responses varied by individual whales, with Nemo seeming to be on one end of the spectrum, apparently thrown into a frenzy when the Lauge Koch came near and when the gun was firing. Siggi’s acoustic storyboard looked almost identical to Nemo’s, for a time. Satellite data show that the young males travelled together for two days after they were tagged. But, on August 26th, as the Lauge Koch passed near them, Siggi headed north, away from the southeast-bound ship, whereas Nemo seemed to panic: he headed right back into a Hjørnedal net and was separated from his companion. The team immediately let him go and the hunters were paid a second time. On August 27th, the same thing happened: Nemo swam into a net and was again released. No one wanted to put another heart-rate recorder on Nemo either time, Blackwell said. “He is a bit of a hyper whale.” Nemo finally swam far from Hjørnedal and found Siggi in front of Syd Brae.

Capturing the whales has adverse effects, findings published by the team in the journal Science in 2017 show. Readings from five narwhals, none apparently as talented as Nemo at removing the heart-rate monitor, showed that the animals have what is called a paradoxical escape response. After being caught, tagged, and released, their heart rate plummeted as it would for a deep dive at the same time that their swim speed increased for escape, rapid stroking that required the heart to pump more. The researchers worry that this “cardiac freeze” response might be triggered not just by the comparatively rare and short-lived event of a catch and release but by two other stresses: new predators, such as killer whales, which are starting to colonize narwhal habitats as the water warms, and anthropogenic noise. Another study led by Terrie Williams of the University of California, Santa Cruz, who was the lead author of the 2017 study, is due out this fall; it will reveal whether the air-gun pulses and the ship affected the narwhals’ heart rate.

Air guns are not likely to be heard soon in Scoresby Sound—nearby petroleum leases sit just to the north, on Jameson Land, and the government of Greenland recently announced a ban on new oil-and-gas leases. But the researchers’ findings could have implications for resource exploration and extraction elsewhere, particularly in the Canadian Arctic. And vessel noise is rapidly increasing: it was up forty-four per cent in the Northwest Passage between 2013 and 2019, and some research suggests that it could grow by as much as five hundred per cent in the next few years. Before the pandemic, a dozen or so companies had begun to offer cruise tours of Scoresby Sound and East Greenland, where passengers could, as one Web site put it, “prepare to be humbled by the magnitude of the landscape.”

In August, 2019, Heide-Jørgensen, Williams, and others returned to Hjørnedal. There were no seismic tests, no vessel-based team. Heide-Jørgensen said the team is confident they have established that the whales—clearly adapted to loud natural sounds—change their behavior in response to the air gun and ship noise. “If this was going on for a long time in an area vital for the narwhal for feeding, for instance, or for social interactions, like mating, that would probably have a negative effect on their fitness and reproduction,” Eva Garde, a member of the team who works for the Greenland Institute of Natural Resources, said. The researchers have pivoted mostly to climate-change studies, and are looking at the effects of warming water on narwhal behavior and physiology. For instance, they tested infrared sensors to understand how narwhals may get rid of potentially lethal excess body heat—vital to their survival as cold- and ice-adapted animals.

The summer of 2019 was, by the researchers’ accounts, a strange one. There were almost no narwhals. Those caught were mostly recaptures—Nemo was not among them. High rates of recapture suggest a small population; because narwhals often show what is called site fidelity, they return to the same place for their entire lives. Also alarming to the team was the fact that all but one of the narwhals caught were male. “So there are less and less females, and those we see, they are not pregnant,” Heide-Jørgensen said. “We have to deal with this situation—that the narwhals are going downhill in East Greenland.”

The dire field observations led to a fall, 2019, meeting of a working group on East Greenland narwhals; the group had been formed a year earlier within the North Atlantic Marine Mammal Commission, which, along with the Canada-Greenland Joint Commission on Narwhal and Beluga, provides advice to the government of Greenland about managing subsistence species. “The population is now being impacted by changes in sea-surface temperature, changes in ice cover, and changes in the local fauna,” Roderick Hobbs, the chair of the working group, and formerly of the National Oceanic and Atmospheric Administration, said. “There has been a hunt that has gone on regularly, and it seemed like the hunt is larger than the population can sustain.” The group’s recommendation was that the annual total allowable catch for the three East Greenland management units—Ittoqqortoormiit, Kangerlussuaq, and Tasiilaq—be reduced from fifty to zero.

For many hunters, this was unacceptable. “We cannot agree with a TAC put to zero,” Tønnes Berthelsen, the former director of K.N.A.P.K., the Association of Fishers and Hunters in Greenland, told me. Berthelsen and a fellow-researcher, Qarsoq Høegh-Dam, also previously employed by K.N.A.P.K., pointed to the challenges of doing accurate population counts of whales in an area as large and largely inaccessible as the Arctic—even as the ice melts, field work remains difficult and costly. “It is not that someone is against biologists; it is just the merits of the data regarding the hunters. Because the hunters live and breathe in the same area where the narwhals are, there needs to be a balance between the biological advice and also the hunters, who have specific training, and their biological advice,” Høegh-Dam told me, earlier this year. “The hunters are finding that the biologists’ advice doesn’t one hundred per cent correspond.”

Last August, the Hjørnedal researchers again returned to the field. They did not tag a single narwhal. A few months later, Heide-Jørgensen and nine other scientists published a letter in Science saying that the East Greenland narwhals were at risk of going locally extinct because of overharvesting and climate change. Five months later, two East Greenland hunters, Åge Hammeken and Tobias Ignatiussen, presented before the North Atlantic Marine Mammal Commission’s cetacean-management committee, saying that they see plenty of narwhals and that the researchers’ data and population assessments are incomplete. Citing, among other things, the discrepancies between the hunters’ and the biologists’ views, and a Greenlandic hunting law requiring that user knowledge be included in regulatory decisions, the management committee did not back the zero-quota recommendation.

The rapidity of the changes in the Arctic has catapulted everyone involved into unfamiliar, unstable terrain. In the last forty years, according to the National Snow and Ice Data Center, the extent and volume of winter sea ice have shrunk by some nine hundred and seventy-five thousand square miles, an area roughly the size of Mexico; summer ice may be gone in as few as two decades. Communities are grappling with how to reconcile subsistence-hunting quotas with climate change. By collaborating with Inuit polar-bear hunters, including some in East Greenland, Kristin Laidre of the University of Washington and other researchers are trying to build rapid habitat change into estimates of carrying capacity, which could then be used by regulators to inform polar-bear quotas. “That has been really key to our research: understanding community perspective, working on the ground in communities, and making sure our science is relevant,” Laidre said. “We want to conserve these populations and maintain healthy populations of animals. At the same time, we also want to be able to maintain their use as a biological resource.”

Nothing similar exists for the narwhal, a species that may prove to be even more vulnerable to climate change than the iconic polar bear. “There is nothing to suggest that narwhals are very flexible, that they will eat many types of prey, that they will change their habits or change their migration routes or change where they feed,” Laidre said. “They are sensitive to noise. They are sensitive to disturbance. They are really strange creatures.” At every public talk she gives on narwhals, people come up to say they didn’t know that these strange creatures truly existed. “That is the one thing they have learned from my presentation: that narwhals are real,” she said.

At least for now. As the ice and the cold of the Arctic vanish, narwhals may be on their way to becoming what many already imagine them to be: fabulous, cryptic creatures that lived, once upon a time, at one end of the earth.