Polar bears in some parts of the high Arctic are developing ice buildup and related injuries to their feet, apparently due to changing sea ice conditions in a warming Arctic. While surveying the health of two polar bear populations, researchers found lacerations, hair loss, ice buildup and skin ulcerations primarily affecting the feet of adult bears as well as other parts of the body. Two bears had ice blocks up to 1 foot (30 centimeters) in diameter stuck to their foot pads, which caused deep, bleeding cuts and made it difficult for them to walk.

The led by the 91̽�� was published Oct. 22 in the journal Ecology. It’s the first time that such injuries have been documented in polar bears.

The researchers suggest several mechanisms for how the shift from a climate that used to remain well below freezing to one with freeze–thaw cycles could be causing ice buildup and injuries.

“In addition to the anticipated responses to climate change for polar bears, there are going to be other, unexpected responses,” said lead author , a senior principal scientist at the 91̽��Applied Physics Laboratory and a professor in the 91̽��School of Aquatic and Fishery sciences. “As strange as it sounds, with climate warming there are more frequent freeze-thaw cycles with more wet snow, and this leads to ice buildup on polar bears’ paws.”

Between 2012 and 2022, Laidre and co-author , a wildlife veterinarian, studied two populations of polar bears living above 70 degrees north latitude and saw the injuries.

In the Kane Basin population, located between Canada and Greenland, 31 of 61 polar bears showed evidence of icing-related injuries, such as hairless patches, cuts or scarring.

In the second population in East Greenland, 15 of 124 polar bears had similar injuries. Two Greenland bears at separate locations in 2022 had massive ice balls stuck to their feet.

“I’d never seen that before,” Laidre said. “The two most-affected bears couldn’t run — they couldn’t even walk very easily. When immobilizing them for research, we very carefully removed the ice balls. The chunks of ice weren’t just caught up in the hair. They were sealed to the skin, and when you palpated the feet it was apparent that the bears were in pain.”

Researchers have studied these two polar bear populations since the 1990s but haven’t reported these types of injuries before. Consultations with lifetime Indigenous subsistence hunters and a survey of the scientific literature suggests this is a recent phenomenon.

Polar bears have small bumps on their foot pads that help provide traction on slippery surfaces. These bumps, which are larger than those on the pads of other bear species like brown and black bears, make it easier for wet snow to freeze to the paws and accumulate. This problem also affects sled dogs in the North.

The authors hypothesize three possible reasons for increasing ice buildup on polar bears’ paws — all related to climate warming. One is more rain-on-snow events, which creates moist, slushy snow that clumps onto paws and then freezes to form a solid once temperatures drop.

A second possibility is that more warm spells are causing the surface snow to melt and then refreeze into a hard crust. The heavy polar bears break through this ice crust, cutting their paws on its sharp edges.

The final possible reason is that both these populations live on “” connected to the land, near where freshwater glaciers meet the ocean. Warming in these environments leads to thinner sea ice, allowing seawater to seep up into the snow. This wet snow can clump onto bears’ feet and then refreeze to form ice. Also, unlike other areas, polar bears living at glaciers’ edges rarely swim long distances in spring, which would help thaw and dislodge accumulated ice chunks because the water is warmer than the air.

While the bears are clearly affected by the ice buildup, the researchers are cautious regarding broader conclusions about the health of the two populations.

“We’ve seen these icing-related injuries on individual polar bears,” Laidre said. “But I would hesitate to jump to conclusions about how this might affect them at a population level. We really don’t know.”

, a research scientist at UW’s Applied Physics Laboratory, recently published a separate analyzing snow cover on Arctic sea ice over recent decades.

“The surface of Arctic sea ice is transforming with climate change,” Webster said. “The sea ice has less snow in late spring and summer, and the snow that does exist is experiencing earlier, episodic melt and more frequent rain. All these things can create challenging surface conditions for polar bears to travel on.”

Asked what can be done to help the polar bears, Laidre had a simple response: “We can reduce greenhouse gas emissions and try to limit climate warming.”

The field observations of polar bears were funded by the governments of Canada, Denmark, Nunavut and Greenland. Laidre is also affiliated with the Greenland Institute of Natural Resources.

For more information, contact Laidre at klaidre@uw.edu.

Scientists have documented a previously unknown subpopulation of polar bears living in Southeast Greenland. The polar bears survive with limited access to sea ice by hunting from freshwater ice that pours into the ocean from Greenland’s glaciers. Because this isolated population is genetically distinct and uniquely adapted to its environment, studying it could shed light on the future of the species in a warming Arctic.

“We wanted to survey this region because we didn’t know much about the polar bears in Southeast Greenland, but we never expected to find a new subpopulation living there,” said lead author , a polar scientist at the 91̽��’s Applied Physics Laboratory. “We knew there were some bears in the area from historical records and Indigenous knowledge. We just didn’t know how special they were.”

The , published in the June 17 issue of Science, combines seven years of new data collected along the southeastern coast of Greenland with 30 years of historical data from the island’s whole east coast. The remote Southeast region had been poorly studied because of its unpredictable weather, jagged mountains and heavy snowfall. The newly collected genetic, movement and population data show how these bears use glacier ice to survive with limited access to sea ice.

“Polar bears are threatened by sea ice loss due to climate change. This new population gives us some insight into how the species might persist into the future,” said Laidre, who is also a 91̽��associate professor of aquatic and fishery sciences. “But we need to be careful about extrapolating our findings, because the glacier ice that makes it possible for Southeast Greenland bears to survive is not available in most of the Arctic.”

The genetic difference between this group of bears and its nearest genetic neighbor is greater than that observed for any of the 19 previously known polar bear populations.

“They are the most genetically isolated population of polar bears anywhere on the planet,” said co-author , a professor and geneticist at the University of California, Santa Cruz and investigator at the Howard Hughes Medical Institute. “We know that this population has been living separately from other polar bear populations for at least several hundred years, and that their population size throughout this time has remained small.”

Part of the reason the population is so isolated, researchers believe, is that the bears are hemmed in on all sides: by the sharp mountain peaks and massive Greenland Ice Sheet to the west, the open water of the Denmark Strait to the east, and by the fast-flowing East Greenland coastal current that poses a hazard offshore.

Before starting the fieldwork, the team spent two years soliciting input and gathering information from polar bear subsistence hunters in East Greenland. Hunters participated throughout the study, contributing their expertise, and providing harvest samples for genetic analysis.

The satellite tracking of adult females shows that, unlike most other polar bears that travel far over sea ice to hunt, Southeast Greenland bears are homebodies. They walk on ice inside protected fjords or scramble up mountains to reach neighboring fjords over the Greenland Ice Sheet. Half of the 27 tracked bears accidentally floated an average of 120 miles (190 kilometers) south on small ice floes caught in the East Greenland coastal current, but then hopped off and walked back north on land to their home fjord.

“In a sense, these bears provide a glimpse into how Greenland’s bears may fare under future climate scenarios,” Laidre said. “The sea ice conditions in Southeast Greenland today resemble what’s predicted for Northeast Greenland by late this century.”

Southeast Greenland bears have access to sea ice for only four months, between February and late May. Sea ice provides the platform that most of the Arctic’s roughly 26,000 polar bears use to hunt seals. But polar bears can’t fast for eight months. For two-thirds of the year, the Southeast Greenland polar bears rely on a different strategy: They hunt seals from chunks of freshwater ice breaking off the Greenland Ice Sheet.

“The marine-terminating glaciers in Southeast Greenland are a fairly unique environment,” said co-author , deputy lead scientist at the National Snow and Ice Data Center. “These types of glaciers do exist in other places in the Arctic, but the combination of the fjord shapes, the high production of glacier ice and the very big reservoir of ice that is available from the Greenland Ice Sheet is what currently provides a steady supply of glacier ice.”

The fact that bears can survive here suggests that marine-terminating glaciers, and especially those regularly calving ice into the ocean, could become small-scale climate refugia — places where some polar bears could survive as sea ice on the ocean’s surface declines. Similar habitats exist at marine-terminating glaciers on other parts of Greenland’s coast and the island of Svalbard, a Norwegian territory located east of Greenland.

“Even with rapid changes happening on the ice sheet, this area in Greenland has the potential to continue to produce glacial ice, with a coast that may looks similar to today, for a long time,” Moon said.

The authors estimate that there are roughly a few hundred bears in Southeast Greenland, similar to other small populations. Body measurements suggest that adult females are smaller than in most regions. They also have fewer cubs, which may reflect the challenge of finding mates in the complex landscape of fjords and mountains. Laidre cautioned, however, that longer-term monitoring is needed to know the future viability of Southeast Greenland bears and to understand what happens to polar bear subpopulations as they become increasingly cut off from the rest of the Arctic by declining sea ice.

“If you’re concerned about preserving the species, then yes, our findings are hopeful — I think they show us how some polar bears might persist under climate change,” Laidre said. “But I don’t think glacier habitat is going to support huge numbers of polar bears. There’s just not enough of it. We still expect to see large declines in polar bears across the Arctic under climate change.”

The government of Greenland will decide on any protection and management measures. The International Union for Conservation of Nature, which helps oversee protected species, is responsible for determining whether Southeast Greenland bears are internationally recognized as a separate population, the 20th in the world.

“Preserving the genetic diversity of polar bears is crucial going forward under climate change,” Laidre said. “Officially recognizing these bears as a separate population will be important for conservation and management.”

This research was funded by NASA, the U.S. National Science Foundation, the government of Denmark; the government of Greenland; the UW; the University of Oslo; the Leo Model Foundation and the Vetlesen Foundation. Other co-authors are Eric Regehr, Benjamin Cohen and Harry Stern at the UW; Megan Supple, Christopher Vollmers and Russ Corbett-Detig at UC Santa Cruz; Erik Born, Fernando Ugarte, Peter Hegelund and Carl Isaksen at the Greenland Institute of Natural Resources; Oystein Wiig at the University of Oslo; Jon Aars at the Norwegian Polar Institute; Rune Dietz and Christian Sonne at Arhus University in Denmark; Geir Akse, a helicopter pilot in Norway; and David Paetkau at Wildlife Genetics International in Canada.

In a rapidly changing Arctic, one area might serve as a refuge – a place that could continue to harbor ice-dependent species when conditions in nearby areas become inhospitable. This region north of Greenland and the islands of the Canadian Arctic Archipelago has been termed the Last Ice Area. But research led by the 91̽�� suggests that parts of this area are already showing a decline in summer sea ice.

Last August, sea ice north of Greenland showed its vulnerability to the long-term effects of climate change, according to a published July 1 in the open-access journal .

“Current thinking is that this area may be the last refuge for ice-dependent species. So if, as our study shows, it may be more vulnerable to climate change than people have been assuming, that’s important,” said lead author , a polar scientist at the 91̽��Applied Physics Laboratory.

How the last ice-covered regions will fare matters for polar bears that use the ice to hunt for seals that use the ice for building dens for their young, and for walruses that use the ice as a platform for foraging.

“This area has long been expected to be the primary refuge for ice-dependent species because it is one of the last places where we expect summer sea ice to survive in the Arctic,” said co-author , a principal scientist at the 91̽��Applied Physics Laboratory.

The study focused on sea ice in August 2020 in the Wandel Sea, an area that used to be covered year-round in thick, multiyear ice.

“Sea ice circulates through the Arctic, it has a particular pattern, and it naturally ends up piling up against Greenland and the northern Canadian coast,” Schweiger said. “In climate models, when you spin them forward over the coming century, that area has the tendency to have ice survive in the summer the longest.”

Like other parts of the Arctic Ocean, the ice here has been gradually thinning, though last spring’s sea ice in the Wandel Sea was on average slightly thicker than previous years. But satellite images showed a record low of just 50% sea ice concentration on Aug. 14, 2020.

The new study uses satellite data and sea ice models to determine what caused last summer’s record low. It finds that about 80% was due to weather-related factors, like winds that break up and move the ice around. The other 20%, or one-fifth, was from the longer-term thinning of the sea ice due to global warming.

The model simulated the period from June 1 to Aug. 16 and found that unusual winds moved sea ice out of the area, but that the multiyear thinning trend also contributed, by allowing more sunlight to warm the ocean. Then, when winds picked up, this warm water was able to melt the nearby ice floes.

The record-low ice concentration in 2020 was surprising because the average ice thickness at the beginning of summer was actually close to normal.

“During the winter and spring of 2020 you had patches of older, thicker ice that had drifted into there, but there was enough thinner, newer ice that melted to expose open ocean,” Schweiger said. “That began a cycle of absorbing heat energy to melt more ice, in spite of the fact that there was some thick ice. So in years where you replenish the ice cover in this region with older and thicker ice, that doesn’t seem to help as much as you might expect.”

The results raise concerns about the Last Ice Area but can’t immediately be applied to the entire region, Schweiger said. Also unknown is how more open water in this region would affect ice-dependent species over the short and long terms.

“We know very little about marine mammals in the Last Ice Area,” said Laidre, who is also an associate professor in the School of Aquatic and Fishery Sciences. “We have almost no historical or present-day data, and the reality is that there are a lot more questions than answers about the future of these populations.”

Other co-authors are Michael Steele and Jinlun Zhang at the UW; and Kent Moore at the University of Toronto. The research was funded by the U.S. National Science Foundation, NASA, the Natural Sciences and Engineering Research Council of Canada; the National Oceanic and Atmospheric Administration; the Office of Naval Research; and the World Wildlife Fund Canada.

For more information, contact Schweiger at schweig@uw.edu, Steele at mas@apl.washington.edu or Laidre at klaidre@uw.edu. Note: Schweiger is on Central European Time. Steele and Laidre are on Pacific Time.

A small subpopulation of polar bears lives on what used to be thick, multiyear sea ice far above the Arctic Circle. The roughly 300 to 350 bears in Kane Basin, a frigid channel between Canada’s Ellesmere Island and Greenland, make up about 1-2% of the world’s polar bears.

New research shows that Kane Basin polar bears are doing better, on average, in recent years than they were in the 1990s. The , published Sept. 23 in Global Change Biology, finds the bears are healthier as conditions are warming because thinning and shrinking multiyear sea ice is allowing more sunlight to reach the ocean surface, which makes the system more ecologically productive.

“We find that a small number of the world’s polar bears that live in multiyear ice regions are temporarily benefiting from climate change,” said lead author , a polar scientist at the 91̽�� Applied Physics Laboratory’s Polar Science Center.

If greenhouse gases continue to build up in the atmosphere and the climate keeps warming, within decades these polar bears will likely face the same fate as their southern neighbors already suffering from declining sea ice.

“The duration of these benefits is unknown. Under unmitigated climate change, we expect the Kane Basin bears to run into the same situation as polar bears in the south — it’s just going to happen later,” Laidre said. “They’ll be one of the last subpopulations that will be negatively affected by climate change.”

All of the world’s 19 polar bear subpopulations, including Kane Basin, are experiencing a shorter on-ice hunting season, according to a 2016 study led by Laidre. This makes it hard for the animals, that can weigh more than 1,200 pounds as adults, to meet their nutritional needs. Polar bears venture out on sea ice to catch seals. In summer when the sea ice melts, the polar bears fast on land.

Laidre led a recent study showing that in the Baffin Bay polar bear subpopulation, which includes about 2,800 bears living just south of Kane Basin, adult females are thinner and are having fewer cubs as the summer open-water season —  when they must fast on land —  grows longer.

“Kane Basin is losing its multiyear ice, too, but that doesn’t have the same effect on the polar bears’ ability to hunt,” Laidre said. “Multiyear ice becomes annual ice, whereas annual ice becomes open water, which is not good for polar bears.”

The new paper looked at Kane Basin bears using satellite tracking data and direct physical measurements to compare from 1993 to 1997 with a more recent period, from 2012 to 2016. The body condition, or fatness, improved for all ages of males and females. The average number of cubs per litter, another measure of the animals’ overall health, was unchanged.

Satellite tags showed the Kane Basin polar bears traveled across larger areas in recent years, covering twice as much distance and ranging farther from their home territory.

“They now have to move over larger areas,” Laidre said. “The region is transitioning into this annual sea ice that is more productive but also more dynamic and broken up.”

Observations show a profound shift in the sea ice in Kane Basin between the two study periods. In the 1990s, about half the area was covered in multiyear ice in the peak of summer, while in the 2010s the region was almost completely annual ice, which melts to open water in summer.

Even though there’s now more open water, the marine ecosystem has become more productive. Annual sea ice allows more sunlight through, so more algae grow, which supports more fish and in turn attracts seals.

“Two decades ago, scientists hypothesized that climate change could temporarily benefit polar bears in multiyear ice regions over the short term, and our observations support that,” Laidre said.

The subpopulation on the other side of Ellesmere Island, in Canada’s Norwegian Bay, could be in a similar situation, she said, though no data exist for those animals.

If conditions continue to warm these northernmost polar bears will likely face the same fate as their southern neighbors. Kane Basin polar bears have only much deeper water to turn to farther north.

“It’s important not to jump to conclusions and suggest that the High Arctic, which historically was covered by multiyear sea ice, is going to turn into a haven for polar bears,” said Laidre, who is also an associate professor in the 91̽��School of Aquatic and Fishery Sciences. “The Arctic Ocean around the North Pole is basically an abyss, with very deep waters that will never be as productive as the shallower waters to the south where most polar bears live.

“So we are talking about temporary benefits in a limited area and to a very small number of bears.”

Co-authors are , , and at the UW; and Markus Dyck with the Government of Nunavut in Canada; Erik Born with the Greenland Institute of Natural Resources; at the University of Oslo in Norway; and , with Environment and Climate Change Canada.

Major funders include the governments of Canada, Denmark, Nunavut and Greenland; NASA; and the World Wildlife Fund.

For more information, contact Laidre at klaidre@uw.edu.

NASA grant: NNX13AN28G NNX11A063G

Polar bears are spending more time on land than they did in the 1990s due to reduced sea ice, new 91̽��-led research shows. Bears in Baffin Bay are getting thinner and adult females are having fewer cubs than when sea ice was more available.

The , recently published in Ecological Applications, includes satellite tracking and visual monitoring of polar bears in the 1990s compared with more recent years.

“Climate-induced changes in the Arctic are clearly affecting polar bears,” said lead author , a 91̽��associate professor of aquatic and fishery sciences. “They are an icon of climate change, but they’re also an early indicator of climate change because they are so dependent on sea ice.”

The international research team focused on a subpopulation of polar bears around Baffin Bay, the large expanse of ocean between northeastern Canada and Greenland. The team tracked adult female polar bears’ movements and assessed litter sizes and the general health of this subpopulation between the 1990s and the period from 2009 to 2015.

Polar bears’ movements generally follow the annual growth and retreat of sea ice. In early fall, when sea ice is at its minimum, these bears end up on Baffin Island, on the west side of the bay. They wait on land until winter when they can venture out again onto the sea ice.

When Baffin Bay is covered in ice, the bears use the solid surface as a platform for hunting seals, their preferred prey, to travel and even to create snow dens for their young.

“These bears inhabit a seasonal ice zone, meaning the sea ice clears out completely in summer and it’s open water,” Laidre said. “Bears in this area give us a good basis for understanding the implications of sea ice loss.”

Satellite tags that tracked the bears’ movements show that polar bears spent an average of 30 more days on land in recent years compared to in the 1990s. The average in the 1990s was 60 days, generally between late August and mid-October, compared with 90 days spent on land in the 2000s. That’s because Baffin Bay sea ice retreats earlier in the summer and the edge is closer to shore, with more recent summers having more open water.

“When the bears are on land, they don’t hunt seals and instead rely on fat stores,” said Laidre. “They have the ability to fast for extended periods, but over time they get thinner.”

To assess the females’ health, the researchers quantified the condition of bears by assessing their level of fatness after sedating them, or inspecting them visually from the air. Researchers classified fatness on a scale of 1 to 5. The results showed the bears’ body condition was linked with sea ice availability in the current and previous year — following years with more open water, the polar bears were thinner.

The body condition of the mothers and sea ice availability also affected how many cubs were born in a litter. The researchers found larger litter sizes when the mothers were in a good body condition and when spring breakup occurred later in the year — meaning bears had more time on the sea ice in spring to find food.

The authors also used mathematical models to forecast the future of the Baffin Bay polar bears. The models took into account the relationship between sea ice availability and the bears’ body fat and variable litter sizes. The normal litter size may decrease within the next three polar bear generations, they found, mainly due to a projected continuing sea ice decline during that 37-year period.

“We show that two-cub litters — usually the norm for a healthy adult female — are likely to disappear in Baffin Bay in the next few decades if sea ice loss continues,” Laidre said. “This has not been documented before.”

Laidre studies how climate change is affecting polar bears and other marine mammals in the Arctic. She led a 2016 study showing that polar bears across the Arctic have less access to sea ice than they did 40 years ago, meaning less access to their main food source and their preferred den sites. The new study uses direct observations to link the loss of sea ice to the bears’ health and reproductive success.

“This work just adds to the growing body of evidence that loss of sea ice has serious, long-term conservation concerns for this species,” Laidre said. “Only human action on climate change can do anything to turn this around.”

Co-authors of the study are and at the UW; and at the Government of Nunavut in Canada; at the Greenland Institute of Natural Resources; at the Natural History Museum in Norway; and of Environment and Climate Change Canada. Main funders of the research include NASA and the governments of Nunavut, Canada, Greenland, Denmark and the United States.

For more information, contact Laidre at �����������𰪳ܷ�.������or 206-616-9030.

This story is adapted from a .

With 2019 on pace as one of the warmest years on record, a new international study reveals how rapidly the Arctic is warming and examines global consequences of continued polar warming.

The , published Dec. 4 in the journal Science Advances, reports that the Arctic has warmed by 0.75 degrees C in the last decade alone. By comparison, the Earth as a whole has warmed by nearly the same amount, 0.8 C, over the past 137 years.

“Many of the changes over the past decade are so dramatic they make you wonder what the next decade of warming will bring,” said lead author , a University of California, Davis, professor of climate change ecology. “If we haven’t already entered a new Arctic, we are certainly on the threshold.”

What 2 degrees global warming means for the poles

The comprehensive report represents the efforts of an international team of 15 authors, including at the 91̽��, who specialize in an array of disciplines, including the life, Earth, social and political sciences. They documented widespread effects of warming in the Arctic and Antarctic on wildlife, traditional human livelihoods, tundra vegetation, methane release, and loss of sea- and land-ice.

“What’s happening in the Arctic is profound and unprecedented,” said Laidre, a 91̽��research scientist at the Polar Science Center and associate professor in the School of Aquatic and Fishery Sciences. “Marine mammals rely on the sea ice platform for most aspects of their life and it is rapidly disappearing. This has cascading impacts on the ecosystem, species interactions, and indigenous humans who rely on these animals for nutritional, cultural and economic purposes.”

Laidre served as the team’s expert on Arctic marine mammals, bringing together the recent literature on profound changes observed related to species and populations, and linking them to other physical and biological components catalogued by other co-authors.

The research team also examined consequences for the polar regions as the Earth inches toward 2 C warming, a commonly discussed milestone.

“Under a business-as-usual scenario, the Earth as a whole may reach that milestone in about 40 years,” said Post. “But the Arctic is already there during some months of the year, and it could reach 2 C warming on an annual mean basis as soon as 25 years before the rest of the planet.”

The study illustrates what 2 C of global warming could mean for the high latitudes: up to 7 C warming for the Arctic and 3 C warming for the Antarctic during some months of the year.

The authors say that active, near-term measures to reduce carbon emissions are crucial to slowing high latitude warming, especially in the Arctic.

Beyond the polar regions

Post emphasizes that major consequences of projected warming in the absence of carbon mitigation are expected to reach beyond the polar regions. Among these are sea level rise resulting from rapid melting of land ice in the Arctic and Antarctic, as well as increased risk of extreme weather, deadly heat waves, and wildfire in parts of the Northern Hemisphere.

“What happens in the Arctic doesn’t ���ٲ�����in the Arctic,” said co-author , a distinguished professor of atmospheric sciences at Pennsylvania State University. “The dramatic warming and melting of Arctic ice is impacting the jet stream in a way that gives us more persistent and damaging weather extremes.”

Other co-author institutions are Aarhus University; University of Oxford; University of Lapland; University of Colorado, Boulder; Chicago Botanic Garden; Dartmouth College; Umea University; University College London; U.S. Arctic Research Commission; Harvard University; and National Oceanic and Atmospheric Administration (NOAA).

Funding for the study is from the National Science Foundation, Academy of Finland and JPI Climate, National Geographic Society, Natural Environment Research Council, the Swedish Research Council, NASA and NOAA.

This post is adapted from a UC Davis .

Polar bears likely survived past warm periods in the Arctic, when sea ice cover was low, by scavenging on the carcasses of stranded large whales. This food source sustained the bears when they were largely restricted to land, unable to roam the ice in search of seals to hunt.

A new led by the 91̽�� found that although dead whales are still valuable sources of fat and protein for some polar bears, this resource will likely not be enough to sustain most bear populations in the future when the Arctic becomes ice-free in summers, which is likely to occur by 2040 due to climate change. The results were published online Oct. 9 in the journal Frontiers in Ecology and the Environment.

“If the rate of sea ice loss and warming continues unmitigated, what is going to happen to polar bear habitat will exceed anything documented over the last million years. The extremely rapid pace of this change makes it almost impossible for us to use history to predict the future,” said lead author , a marine biologist at the UW’s Polar Science Center and associate professor in the School of Aquatic and Fishery Sciences.

Polar bears need sea ice to survive because it is an essential platform for hunting seals, their main food source. They travel over the ice, searching for breathing holes or seal birth dens. When the ice breaks up in late spring, polar bears in some populations will fast on land, waiting for the ice to re-form so they can resume hunting.

Still, polar bears are opportunistic feeders and have been observed in multiple locations eating the carcasses of whales that died at sea and washed ashore. The bears can quickly consume and store large amounts of fat, which works in their favor. In some cases, between 40 and 60 different polar bears have been observed feeding on large bowhead and gray whale carcasses and, in 2017, more than 180 bears were seen scavenging on a single dead bowhead whale. Individual bears frequently return to the same carcass over multiple years.

The authors drew upon years of observations in the field to assess the potential importance of whale carcasses and how they might help polar bears survive an ice-free Arctic. It is clear that polar bears persisted through low-ice interglacial periods in the past that resulted from naturally occurring climate cycles. The researchers hypothesized that, to a significant degree, the bears likely survived by scavenging on whale carcasses, storing large amounts of fats when hunting seals was not an option.

“I think this is likely one of the most probable explanations for how polar bears made it through previous warm interglacial periods,” said co-author , former research scientist with the Canadian Department of Environment and an adjunct professor at the University of Alberta, who has studied polar bears for 45 years.

“But when we look at the situation now, ecologically, with respect to food sources, it’s a very different picture,” Stirling added. “The potential of whale carcasses to bail bears out may still be important in a few areas but, quite simply, their overall availability is going to be substantially less than before humans invaded the Arctic.”

The researchers wanted to determine whether enough large whales dying and washing ashore each year could replace seals as a food source for polar bears in some areas. They first calculated how much blubber and meat an average population of 1,000 polar bears would need as a food source each year.

Then, they looked at the abundance of gray and bowhead whale populations — focusing on the coasts of Chukotka and Alaska — and estimated the number of potential strandings, factoring in that about 10 percent of whales that die will float to the surface, and only some of those end up on land that is accessible to bears.

Their analysis found that during ice-free summer months, a hypothetical population of 1,000 polar bears would need to eat about eight whales, and during the springtime feast when bears eat more, about 20 whales would be needed to satisfy the same 1,000 bears. In the Chukchi Sea, long-term data collected in Russia indicate that enough whales die and float to shore each year to potentially meet this need, the authors found.

But feeding on dead whales, while possibly critical in historical times, seems unlikely to help most polar bear populations survive a rapidly warming Arctic. The Arctic is home to , but not every region sees large whales strand and die as regularly as the Chukchi Sea. Additionally, though whale carcasses likely helped polar bears survive in past low-ice periods, the Arctic landscape has changed drastically since then. Present-day whale populations are much smaller due to past human exploitation, and recent human activity in the region such as shipping, coastal communities and offshore industrial activity can further impact polar bears, whales, and the ability of bears to make use of whale carcasses.

“Scavenging on large whale carcasses is probably important for bears in some areas and may buffer them from sea ice loss,” Laidre said. “However, carcasses of large whales are not expected to replace seals as nutritional resources as we move towards an ice-free Arctic. In most regions, the environmental changes are too large and the whale carcasses are too few.”

Other co-authors are James Estes of the University of California, Santa Cruz, Anatoly Kochnev of the Russian Academy of Sciences, and Jason Roberts of Jason Roberts Productions.

###

For more information, contact Laidre at klaidre@uw.edu and Stirling at 780-993-5380 or ian.stirling@ualberta.ca.

In August 2016, the first traveled through the Northwest Passage, the northern waterway linking the Atlantic and Pacific oceans. The following year, the first plied the Northern Sea Route, a path along Russia’s Arctic coast that was, until recently, impassable by unescorted commercial vessels.

In recent decades parts of the Arctic seas have become increasingly ice-free in late summer and early fall. As sea ice is expected to continue to recede due to climate change, seasonal ship traffic from tourism and freight is projected to rise. A study from the 91̽�� and the University of Alaska Fairbanks is the first to consider potential impacts on the marine mammals that use this region during fall and identify which will be most vulnerable.

The is published the week of July 2 in the .

“We know from more temperate regions that vessels and whales don’t always mix well, and yet vessels are poised to expand into this sensitive region,” said lead author , who did the research as a postdoctoral researcher at the 91̽��and is now a research assistant professor at the University of Alaska Fairbanks. “Even going right over the North Pole may be passable within a matter of decades. It raises questions of how to allow economic development while also protecting Arctic marine species.”

The study looked at 80 subpopulations of the seven marine mammals that live in the Arctic and identified their risks on or near major shipping routes in September, a month when the Arctic Ocean has the most open water.

Forty-two of these subpopulations would be exposed to vessel traffic, and the degree of exposure plus the particular characteristics of each species determine which are most sensitive.

The most vulnerable marine mammals were found to be , or tusked whales. These animals migrate through parts of the Northwest Passage to and from their summertime habitats.

“Narwhals have all the traits that make them vulnerable to vessel disturbances — they stick to really specific areas, they’re pretty inflexible in where they spend the summer, they live in only about a quarter of the Arctic, and they’re smack dab in the middle of shipping routes,” said co-author , a polar scientist at 91̽��Applied Physics Laboratory’s Polar Science Center. “They also rely on sound, and are notoriously skittish and sensitive to any kind of disturbance.”

Other mammals found to be vulnerable were beluga and bowhead whales. Walruses also were vulnerable because some populations are relatively small and known to live along shipping routes, compared to generally large and widely distributed populations of ringed and bearded seals, which were shown to be less vulnerable.

The study found the least vulnerable animals were polar bears, which are largely on land during September, and don’t rely on underwater sound for communication or navigation. Shipping in other seasons may have a greater impact.

The paper also identified two “pinch points,” narrow passageways where ships and animals are most likely to intersect. These are the Bering Strait that separates the U.S. and Russia, and Lancaster Sound in the northern Canadian territory of Nunavut. These regions had a risk of conflicts two to three times higher than on other parts of the shipping route.

“These obligatory pinch points are used by migratory species to get in and out of the Arctic, but they are also necessary passageways for vessels using these sea routes,” Hauser said. “Identifying the relative risks in Arctic regions and among marine mammals can be helpful when establishing strategies to deal with potential effects.”

Travel through the Arctic Ocean is already beginning, with the Russian route having the most potential for commercial ships. The Northern Sea Route had more than 200 ships from 2011 to 2016, all of which were large vessels. More than 100 vessels passed through the Northwest Passage during that time, with more than half being small, private vessels like personal yachts.

The International Maritime Organization in May established the . The voluntary code was proposed by the U.S. and Russia to identify safe routes through the Bering Strait.

The new study could help to create future guidelines, prioritize different measures to protect marine mammals and identify areas needing further study, the authors said.

“I think we can learn a lot from areas that have already been thinking about these kinds of conflicts between ships and marine mammal populations — for example the North Atlantic right whale, or fin and blue whales around California,” Laidre said. “We could aim to develop some mitigation strategies in the Arctic that help ships avoid key habitats, adjust their timing taking into account the migration of animals, make efforts to minimize sound disturbance, or in general help ships detect and deviate from animals.”

The study was funded by NASA and the Collaborative Alaskan Arctic Studies Program. The other co-author is , a polar scientist at the 91̽��Applied Physics Laboratory. Laidre is also a 91̽��associate professor of aquatic and fishery sciences.

###

For more information, contact Hauser at dhauser2@alaska.edu or 907-474-1553 and Laidre at klaidre@uw.edu or 206-616-9030.

NASA grant: NNX16AG33G

Few people have spent as much time studying mammals in the Arctic as , a 91̽�� polar scientist and expert on marine mammals.

One exception would be Inuit subsistence hunters, who for generations have relied on these mammals for nutritional, economic and cultural reasons. A new documents the experience of these hunters and what it might show about changing conditions for polar bears on Greenland’s east coast.

“Our research was motivated by the importance of obtaining local perspectives from subsistence hunters in East Greenland about the subpopulation of polar bears,” said Laidre, who is corresponding author on the paper. “There had not been an interview study for several decades, so a new interview survey was important to conduct, especially before starting an assessment of the subpopulation.”

She will be involved in the assessment over the coming years, which will be the first of its kind for the East Greenland polar bears.

Interviews led and conducted by the Greenland government gathered Inuit perspectives on hunting practices and management from full-time polar bear hunters, the only people allowed to hunt polar bears, in two communities along Greenland’s eastern coast. Tasiilaq is a community of about 3,000 people with 68 full-time polar bear hunters, and Ittoqqortoormiit is a community of less than 400 with 12 full-time polar bear hunters.

Questions covered hunting strategies and the effects of polar bear subsistence quotas introduced in 2006. The scientific aim was to gain an understanding of how climate change is affecting the polar bear subsistence hunt, and to document observed changes in polar bear distribution, numbers and biology over the past two decades.

A local partner interviewed 25 hunters, all men between the ages of 20 and 64, between December 2014 and March 2015. The interviews conducted in Greenlandic were conversational in nature, lasted about two hours on average, and were mostly held in people’s homes.

The last such survey in eastern Greenland was conducted in the 1990s. Other places, including Greenland’s west coast and the Canadian Arctic, have had more recent interview surveys.

Results of the East Greenland survey, when compared with similar questions in the 1990s, show that the hunt has shifted from being done from land to being done from boats, coinciding with reports that the ice-covered routes are becoming more treacherous.

Other , recently published in Frontiers in Marine Science, show that the hunt is happening earlier in the year than it did in the 1990s, with fewer people hunting in the summer months. About 80 percent of hunters in both communities also reported that polar bears are entering communities more often than in the past. Some hunters believed that there were more polar bears because of the quotas introduced in 2006, while others reported that the loss of sea ice is encouraging polar bears to stay closer to shore.

“Subsistence hunters provide an important perspective on the system that needs to be documented and included in the conservation and management of polar bears,” Laidre said.

Co-authors on the paper are at the 91̽��Applied Physics Laboratory and at the Greenland Institute of Natural Resources. The research was funded by the Danish Ministry of Environment.

###

For more information, contact Laidre at klaidre@uw.edu.

Adapted from a by Frontiers in Marine Ecology.

Reductions in sea ice in the Arctic have a clear impact on animals such as polar bears that rely on frozen surfaces for feeding, mating and migrating. But sea ice loss is changing Arctic habitat and affecting other species in more indirect ways, new research finds.

Beluga whales that spend summers feeding in the Arctic are diving deeper and longer to find food than in earlier years, when sea ice covered more of the ocean for longer periods, according to a new analysis led by 91̽�� researchers. The , published this month in the journal Diversity and Distributions, is one of the first to consider the indirect effects of sea ice loss on Arctic species that dwell near the ice, but don’t necessarily depend on it for survival.

“I think this paper is novel in that we’re presenting some of the first indirect effects of sea ice loss for an Arctic whale species,” said lead author , a postdoctoral researcher at the UW’s Polar Science Center and former doctoral student at the School of Aquatic and Fishery Sciences. “As changes in sea ice affect oceanographic properties, that could be affecting the distribution, abundance or species composition of prey for belugas.”

Two genetically distinct beluga populations spend winters in the Bering Sea, then swim north in the early summer as sea ice melts and open water allows them passage into the Beaufort and Chukchi seas. There they feast all summer on fish and invertebrates before traveling back south in the fall. Both populations are considered healthy.

The researchers analyzed migration data collected intermittently from two different periods — referred to in the paper as “early” and “late” — for two beluga populations, covering the years 1993-2002 and 2004-2012. Satellite-linked tags attached to the whales tracked their movements around and away from the high Arctic feeding grounds. Dive-depth data were collected for only one population, the Chukchi belugas, because the other population’s tags did not have those capabilities.

Researchers also tracked sea ice cover in the Arctic over these two periods and found that the ice declined substantially from the first to the second period.

“We have documented loss of sea ice and reductions of habitat for Arctic marine mammals across most of the circumpolar Arctic, so this area is not unique,” said co-author , a 91̽��associate professor in the School of Aquatic and Fishery Sciences and the Polar Science Center. “We’re seeing this ice loss broadly in all areas where belugas occur.”

Sea ice loss appears to affect how the Chukchi belugas dove for their food. During the later period, when there was less sea ice, the whales dove significantly longer and deeper than in the earlier period — presumably in search of prey as the animals, in turn, changed their habits because of different ocean conditions brought on by sea ice loss.

Specifically, during the earlier period belugas dove for 20 minutes or longer only once per day, compared to nearly three times a day during the later period. Similarly, their average daily dive depth increased from about 50 meters (164 feet) to 64 meters (210 feet) between the two periods.

The belugas might be diving longer and deeper to follow prey that has dispersed or been driven deeper itself from changing ocean conditions. It’s also possible that feeding opportunities are actually better for belugas in an ocean with less sea ice.

“Reduced sea ice cover over a longer period of time over the summer could mean improved foraging for belugas,” said Hauser, who is also a researcher at the University of Alaska Fairbanks. “But it’s also important to recognize these changes in diving behavior are energetically costly.”

It’s unclear whether diving changes are positive or negative for belugas, and studies on body condition and health are needed to understand the implications of these changes, she added.

Aside from changes in how belugas dove for food, the nearly two decades of data show that the whales were able to thrive in their summer and fall ocean habitats, despite less ice cover. This adaptability to changes in Arctic conditions speaks to the whales’ resiliency, the researchers said.

“Belugas feed on a lot of different prey and use many different habitats, across open water and dense sea ice and everything in between,” Hauser said. “Because they are such generalists, that could buffer them under climate change.”

Other co-authors are of the UW; Robert Suydam of North Slope Borough in Utqiaġvik, Alaska; and Pierre Richard of Fisheries and Oceans Canada.

This analysis was funded by the National Science Foundation’s 91̽��IGERT Program on Ocean Change, NASA and the 91̽��School of Aquatic and Fishery Sciences. Many individuals and organizations supported beluga whale tagging, including the Alaska Beluga Whale Committee, North Slope Borough, Village of Point Lay, the Inuvialuit Hunter and Trapper Committees, Fisheries and Oceans Canada, National Marine Fisheries Service, Alaska Department of Fish and Game, National Fish and Wildlife Foundation and the Minerals Management Service.

###

For more information, contact Hauser at dhauser@uw.edu or 907-474-1553 and Laidre at klaidre@uw.edu.