The ice that once saved bowhead whales is vanishing beneath them
Populations of bowhead whales were able to hide from hunters under ice, a new study finds, saving them from extinction. But now, climate change is making that refuge disappear.
Between the 17th to early 20th century, thousands of ships sailed the waters of the Arctic. They were hunting bowhead whales (Balaena mysticetus), chasing the gentle giants through the chilly seas.
Whaling ships chased down bowheads to sell their blubber to illuminate factories and to lubricate machinery. They sold their baleen—the stiff brushes that filter the whale’s food in their mouths—to stiffen corsets. Whaling vessels slaughtered more than 250,000 animals between 1530 and 1914, and the animals were hunted to near extinction.
But some whales were able to find refuges, places icy enough to keep hunters at bay. These refuges saved their populations for the future, a new study shows.
In a 2026 study, scientists reconstructed more than 700 whaling trips between 1700 and 1900, and discovered that whales avoided being hunted to extinction by taking refuge in ice-covered areas in summer that whaling vessels couldn’t pierce.
In later years, commercial bowhead hunting was banned, and the huge animals—as long as a 4.5-story building is tall—were officially protected in 1931. Their populations have bounced back.
“The most recent abundance estimates indicate that the population has nearly quadrupled since 1978 and may have reached or surpassed abundance prior to commercial whaling,” says Angela Szesciorka, a marine mammal ecologist at the Pacific Northwest National Laboratory in Seattle, WA.
Whaling is gone, but the bowheads face new threats. Climate change is melting the sea ice they once used for refuge, while big ships increasingly ply the waters of the Arctic. Each of these threatens to disrupt the whales’ long migrations that get underway each spring. Now, again because of humans, bowhead whales may run out of refuges.
Where do bowhead whales migrate—and how climate change is affecting it?
The bowhead whale lives all of its more than 200-year lifespan—the longest life of any mammal—in Arctic waters. Four groups of bowhead whales reside in the Arctic and sub-Arctic regions: the Bering-Chukchi-Beaufort, Eastern Canada-West Greenland, East Greenland-Svalbard-Barents Sea, and the Okhotsk Sea populations.
The Bering-Chukchi-Beaufort group is by far the largest, with more than 17,000 whales. They migrate through the Bering Strait between Canada and Russia in spring, heading about 1,500 kilometers north, and come back south in the fall.
The East Canada-West Greenland group now has about 11,000 whales. As the name suggests, this group travels more than 2,700 kilometers to the far north of Eastern Canada in the summer and back in the fall, straying as far east as Greenland. The last two populations have only a few hundred whales each.
Bowhead whales follow sea ice, moving north as the ice begins to thin and crack. The whales are following the opening ice in search food.
When hunting was at its peak, some the whales found refuge behind areas of thick sea ice where whaling ships couldn’t go, says Nicholas Freymueller, an extinction biologist at Adelaide University in Australia. Freymueller and his colleagues reconstructed the whaling results from more than 700 whaling trips (tracking 72,000 days of whaling) to find out exactly where whales were killed.
The whale populations in Eastern Canada, and off the coast of Alaska in the Bering Sea may have bounced back because they had more refuges avainable, says Freymueller. But the East Greenland- Svalbard- Barents group was hunted for centuries longer than others, while the Okhotsk group had little sea ice to hide behind when whaling ships came calling. That might be why their populations remain so small, he explains.
(Melting ice may be a boon for some Arctic whales)
In their summer feeding grounds, the whales find huge populations of tiny invertebrates, including krill—tiny shrimp-like animals, and copepods—small crustaceans. They open mouths that can be a third of their body length, engulf food-filled water, and strain the food through their thick baleen.
But that migration pattern is changing. In a 2024 study, Szesciorka and her colleagues used sound recording to track where bowhead whales were moving. Bowhead whales, specifically the Bering-Chukchi-Beaufort group, sing nonstop as they migrate north through Bering Strait—the 85 kilometers choke point between Alaska and Russia’s Bering Strait. “This was perfect because the hydrophone just north of Bering Strait could hear any vocalizing animal passing through,” says Szesciorka.
The researchers showed that between 2008 and 2022, bowhead whales changed their travel plans. They started heading south for winter 45 days later. Some are also spending more time in the Beaufort and Chukchi Seas, which could mean there is more food there. And in the winter, some whales are no longer bothering with the Bering Strait, remaining just north in the Chukchi Sea.
Szesciorka says the change is due to a decline in sea ice caused by climate change. “With long-term declines in winter sea ice, whales are remaining further north,” she says. “Minimum sea ice extent has declined by 13 percent per decade since 1979 and sea ice volume has declined by 63 percent since 1982. The Arctic is undergoing rapid change.”
Threats in a busy and noisy ocean
Whaling vessels are gone, but boats are getting more and more busy in the Arctic.
Climate change is reducing sea ice cover, and more open ocean means more ships. “There's been a massive increase in vessel traffic of large scale ships, especially cargo ships, since the advent of online shipping,” says National Geographic Explorer Morgan Martin. Martin is also a marine mammal bioacoustician at the Bureau of Ocean Energy Management in Virginia. “There’s vessel traffic everywhere.”
Some of that traffic is sharing the Bering Strait, and with less sea ice, ships can use the Strait another 20 percent more each year, Szesciorka says. “Traffic has more than doubled between 2013 and 2022.” These large tankers, up to 400 meters long, loom large against a 16-meter whale.
More boats increases the likelihood that ships and whales will run into each other, and so far, Martin has found whales don’t tend to avoid these ships. Martin and other scientists are concerned that with more ships, bowhead whales could face the same fate as the closely-related North Atlantic right whale, for whom boat strikes are the main cause of death.
Boat propellers are also drowning out whale song, which poses another threat to their survival. Bowhead whales are frequenting singers, and they sing low—with most of the energy below one kilohertz. “The baleen whales, we call them low frequency whales, that that's the band that they use most commonly to make sound to find each other,” Martin says.
But in the past few decades, bowheads have gone from swimming in a quiet ocean to a rowdy club, one where it’s hard to hear yourself sing. Passing boats make noise in the same one kilohertz range which bowhead whales sing—making the ocean loud. “The ocean grows a certain number of decibels on average louder every decade,” Martin says. “it can cause what's called acoustic masking,” which is when one sound prevents you hearing another. The noise makes it harder for whales to find one another and keep an ear out for orcas—their most important predator.
Just keep swimming
Now, most people “hunt” the whales on whale-watching cruises. But some Inuit groups are allowed to conduct sustainable hunts for subsistence, and their knowledge of the animals is key for both hunting success and conservation science. “Indigenous communities that rely on bowhead whales for nutritional, cultural, and spiritual subsistence are acutely aware of bowhead whale movement,” Szesciorka says. “Many communities that live and work on the ice and water are often the first ones to notice changes in their movement and behavior.”
(Meet the bowhead whale hunters of northern Alaska)
So more scientists are listening to Inuit groups, and putting more microphones in the water to listen to the whales themselves. This could help them better understand where and when the animals are on the move, and how those movements are changing as sea ice goes down, and boat traffic goes up.
As the sea ice continues to diminish, bowhead whales may no longer have the refuges that saved them in Freymueller’s latest study. “It’s not looking good from a purely climatic perspective, we know that the suitable habitat area across the entire Arctic is projected to decline, believe, 64 to 75 percent depending on moderate to severe carbon emissions,” he says.
And while two of the bowhead whale populations are doing well right now, the other two remain endangered. Every added pressure, from climate change to more ships, could make their lives a little harder.
A species or population going extinct isn’t just the last animal dying, Freymueller says. “Extinction is much better viewed as a pathway, as a process, and the drivers, you know, what sets species on that pathway often begin centuries to millennia before the final population withers away and goes extinct.” What whaling started, other human activities could eventually finish.
But it’s possible the bowhead whales are sensitive enough to noise to move yet again—this time out of the way of shipping lanes. Martin hopes to listen in to find out.
“Either they're going to be like the North Atlantic right whale, and this is going to be really bad for them,” she says, “or they are extremely sensitive to noise, like we believe, and they'll probably try to stay the heck out of the way before the ship is even close to them. That would be the best situation for everyone.”
