It was spring in Alaska’s frozen north, and Todd Atwood was fidgety.
A wildlife biologist and the leader of the U.S. Geological Survey’s polar bear research program, Atwood would normally be in a helicopter, flying over the ice-bound southern Beaufort Sea looking for bears.
Instead, he was planted at his desk in Deadhorse, scrolling through weather reports; poking his head outside to look at the sky and anxiously clicking through various webcams focused on the Arctic coastline.
Retreating sea ice in the Arctic is crippling scientists’ ability to study and monitor polar bears, Atwood and other experts say. The study of the bears, top-of-the-food-chain carnivores with adorable faces, is critical for conservation of the animals and their environment.
Studies show that the decline of sea ice, driven by climate change, is affecting the behavior and physical condition of polar bears, and making it harder for the animals to find enough food to survive. But fallout from global warming also means that Atwood and other researchers have fewer opportunities to hop in a helicopter for forays over the ice. Normally, polar bear scientists track the status of the bears by spotting them from an aircraft, sedating them and landing nearby to conduct a thorough biological examination.
But increasing fog and unstable ice have made such research expeditions dangerous. And even if Atwood and his team are able to fly and succeed in locating a bear, they can only safely spend minutes on the ice instead of hours.
The condition of the sea ice has deteriorated so much that it’s been three years since Atwood and his colleagues have been able to physically examine a bear. When you’re studying polar bears, you need polar bears to study, is Atwood’s mantra.
“The implications are extensive,” he said. “We are losing the ability to track changes in the animals that might foreshadow adverse changes in the population.”
The seasonal window for field research on polar bears in Alaska has narrowed greatly over the last decade. For most of the 36 years USGS scientists have been studying polar bears on the southern Beaufort Sea, the prime time for the research stretched from the end of March to the middle of May, almost two full months when the ice was solid and smooth as a hockey rink. Now the sea ice is melting so quickly that Atwood and his team at the geological survey’s Alaska Science Center are lucky to have three weeks to conduct their research. And the ice is often pock-marked with soft spots—gaping expanses of water or areas with broken ice rubble the size of VW Beetles.
“The lengthening of open water season has caused significant changes in our ability to sample bears,” he said. “The environment in the Arctic is changing faster than the pace of improvements in research.”
A warming climate is likely to have profound effects on polar bears.
A study last year predicted that some of the 19 polar bear subpopulations in the countries that ring the Arctic Circle could suffer devastating declines by the end of the century if climate change continues unchecked.
The less access researchers have to the animals, the less data are collected, and the more difficult it becomes to detect changes in the health of polar bear subpopulations over time, Atwood said.
In addition, there is less information that could give scientists a deeper understanding of how polar bear populations are responding to a variety of climate change stressors, including pathogens, pollutants and contaminants, as well as the effects of sea ice loss on the food chain the bears depend on.
The knowledge gained from such research helps federal and state regulatory agencies establish policies to manage polar bears under U.S. laws and international agreements. Atwood said that recognizing and monitoring health-based threats to polar bears has been identified as priority information needed by wildlife managers.
“The questions that management agencies are asking are increasing,” Atwood said. “The tools we have to answer those questions are decreasing.”
The polar bears studied by Atwood hang out on the ice covering the southern Beaufort Sea, part of the Arctic Ocean north of Alaska and the Northwest Territories, above the Arctic Circle. Researchers have documented the relationship between polar bears and climate change in the south Beaufort subpopulation, which declined by roughly 40 percent from 2005 to 2009.
The South Beaufort, where Atwood does his research, historically has been frozen over for most of the year, with some slivers of ice disappearing near the shores in late summer, usually August and September. But in recent years, the ice-free areas have greatly enlarged, and persisted for longer periods because of climate change. Over the last 25 years, the summer melt period has lengthened by as much as 82 percent, according to USGS studies, and sea ice cover has declined by more than half a million square miles.
The acceleration of sea ice melt results from a combination of warming Pacific Ocean water in the Bering Strait and record high surface air temperatures across the entire Arctic region, said Rick Thoman, a climate specialist with the Alaska Center for Climate Assessment and Policy at the University of Alaska, Fairbanks.
“The water and air temperatures are conspiring to not only reduce the extent of ice in all seasons but also leading to thinning of the ice that remains,” he said.
The substantial decline in sea ice since 1979 is one of the most iconic indicators of climate change, according to the 2020 Arctic Report Card prepared by the National Oceanic and Atmospheric Administration.
And the melting sea ice translates into a shrinking hunting ground for the seals that almost exclusively constitute the polar bears’ diet. The loss of ice has put the bears in the southern Beaufort Sea in the crosshairs of climate change. A study examining changes in sea ice, led by Atwood’s USGS colleague George Durner, concluded that “findings elevate concerns for the future status of SB (Southern Beaufort) polar bears as the transitional seasons of sea ice lengthen and the extent of optimal polar bear habitat during those seasons declines.”
Alaska is one of the fastest warming regions on Earth and is heating up faster than any other U.S. state, according to the Fourth National Climate Assessment, published in 2018. By the middle of the century, the state’s daily maximum temperature could increase by between 4 and 8 degrees Fahrenheit.
The warmer Arctic waters have been linked to polar vortexes, unpredictable severe weather and heatwaves.
That’s on a global front. But in Atwood’s much smaller world the warming means more fog. And more fog means less flying time, because visibility drops to near zero in the dense, sheet-white vapor. By his count, the number of suitable flying days has dropped by more than half over the last 20 years because of fog.
Looking back at flight logs, Atwood said, he found that fog grounded the center’s research helicopters about 24 percent of the time between 2000 and 2009. That number increased to 46 percent between 2010 and 2015; and jumped to 56 percent over the last five years. It correlates with warming temperatures and disappearing sea ice.
“We are losing over half of the time we could be in the air surveying the bears,” he said.
The longstanding protocol for the biological assessments of polar bears calls for sedating the animals with a dart shot from a helicopter, and then waiting for the woozy bear to sprawl on the ice in an incapacitated daze. That procedure normally allowed Atwood and his team about an hour to safely examine the sedated bears, which can weigh as much as 1,500 pounds and stand 10 feet tall on their hind legs.
In that time, researchers could weigh the bear, take a tooth to determine the bear’s age, draw blood, take tissue and fecal samples; and attach a tracking device. Such extensive up-close examination has revealed an increased climate-related vulnerability to pathogens that can weaken a bear’s immune system, according to a 2017 study led by Atwood.
In earlier years, Atwood’s team would physically examine as many as 90 bears a year. “The information that we can obtain from a physical examination gives us the bear’s current state of health, a window into the bear’s future state of health, and the kinds of stressors that are in play with the bears,” Atwood said. “It tells a lot about the bear we have and gives us a good idea of what the bear population is facing.”
But for the researchers, the decline of sea ice has meant taking more risks while at the same time collecting less comprehensive data.
There is always a question whether weakened sea ice can withstand the weight of a 3,000-pound helicopter, its four-member crew and gear.
When the pilot spots ice topped by slushy water it’s a sign the ice is weak, Atwood said. Another clue is when the ice under the bear undulates as the animal moves around.
“When we see the ice flexing under the weight of a bear, obviously we can’t land on it,” Atwood said.
The loss of ice and the corresponding increase in open water is as dangerous for the polar bears as for the researchers. When a bear is shot with a dart, the anesthetizing effects can take up to five minutes. In that time the startled bear can cover hundreds of yards before collapsing, and may try to escape threats by diving into the water.
Atwood said his nightmare scenario is to have a darted bear find open water in its panicked flight, dive in, become incapacitated by the sedative and drown.
“There is far less opportunity to dart a bear now because there are no longer the long stretches of ice we once had where we could safely dart the bear,” he said. “The ice condition dictates what we can do.”
To compensate for the deteriorating conditions that limit physical examination of bears, Atwood and his team now employ a less exhaustive tactic for gathering biological data. When they encounter a bear on a safe stretch of ice, one of the researchers leans out of the helicopter and shoots the animal in the rump with a biopsy dart. Instead of putting the bear to sleep, the sharp dart takes a nip out of the bear’s skin. The sudden pinch surprises the bear, and when it bolts, the dart dislodges and falls onto the ice where it can be retrieved. The helicopter need only be on the ice for a few minutes.
This technique has been employed exclusively since 2019 because of poor ice conditions. Instead of vials of blood and sample jars full of the biological material that come from a physical examination, the dart provides a pencil eraser-sized amount of tissue. Such a small sample limits the amount of information that can be gleaned. Usually, it’s a lipid test that can provide the most information about the bear’s condition. Yet analysis of the biopsied tissue remains just a snapshot.
“It just doesn’t tell us as much as a full physical examination,” Atwood said.
Even this hit-and-run research is hampered by thinning sea ice. This year, Atwood’s team spotted 93 bears from the air. But the ice conditions allowed for darting only 60 of them. In 2019, the numbers were worse. The team sampled 24 of the 52 bears they encountered, letting the others go because of poor ice conditions. “Sometimes when we’re flying over ice that is rotten or surrounded by open water, we hope we don’t see a bear,” he said, “because there is nothing we can do.”
Polar bear biologist Kristin Laidre and her team perform their research more than 2,000 miles from where Atwood does his work. Yet they share the same apprehensions about the disappearing sea ice.
Laidre, a research scientist at the University of Washington’s Polar Science Center, studies polar bears on Baffin Bay, a vast expanse of ocean between northeastern Canada and Greenland that has seen recent declines in sea ice coverage. Although the sea ice retreat is not as dramatic on Baffin Bay as in the southern Beaufort, it has nevertheless forced Laidre and her team to adjust their strategy to account for the changing circumstances.
Like Atwood, Laidre fears that climate-induced changes in the Arctic are affecting polar bears, which depend on sea ice for their survival. And she shares the concern that disappearing and worsening sea ice conditions in the Arctic have combined to severely impede study of the bears, creating a void in information critical to conservation of the animals.
“We can’t rely on ice conditions now that we have had in the past to do our work,” she said.
Laidre, co-author of a recent study that details how declining sea ice is affecting the behavior, health and reproductive success of polar bears, said there has been a drop-off in research capability as the threat to scientists’ safety has increased.
“When you have unsafe conditions on the ice, it means our ability to collect data decreases,” she said. “The less information we collect affects the science we do.”
Laidre and her team are also increasingly dependent on the biopsy dart technique employed by Atwood and his colleagues. But unlike Atwood’s team, they don’t land the helicopter on the ice even for a few minutes to recover the biopsy dart. The copter hovers a few feet over the ice, just close enough to allow a crew member to hop down and grab the dart and then be hauled back into the aircraft.
Ryan Wilson, a biologist with the U.S. Fish and Wildlife Service Marine Mammals Management unit, described ice conditions in the Chukchi Sea that were even worse. Thousands of square miles of ice that once reliably covered the Chukchi, the northern buffer between Alaska and Siberia, has turned to open water or become too unstable to safely allow researcher access to the bears, Wilson said. It’s also unsafe for the biologists to fly over such vast expanses of open water with nowhere to land in an emergency.
Until 2017, Wilson said he and his team relied on physical examination of the bears, and between 2008 and 2017, they averaged examinations of 59 bears a year.
The deterioration of ice conditions was sudden and unexpected, he said, adding that he thought it would be a decade or more before the ice succumbed to the warming temperatures
“It’s striking,” he said. “What I thought would be 20 years happened in five years.”
Wilson and his team must now rely on four-year-old data in their files, information that is becoming staler by the year, for use in the agency’s 2019 Polar Bear Conservation Management Plan, which identifies the primary threats to polar bears and establishes high conservation strategies to promote the survival of the bears.
Although Wilson says his unit can still depend on that dated material to make decisions on polar bear management, those decisions are now incorporating more approximations to fill in the gaps left by the lack of up-to-date information.
“It’s going to become a bigger problem as time goes on,” he said. “If we are not actively updating our information, we might miss changes in the population that leads to mismanagement of the population.”