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 91±¬ÁĎ 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 91±¬ÁĎ Applied Physics Laboratory and a professor in the 91±¬ÁĎ 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 91±¬ÁĎ’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.

, a researcher at the 91±¬ÁĎ Applied Physics Laboratory, appears in the film doing fieldwork on Wrangel Island, an island off the northeast coast of Russia that is home to the world’s highest concentration of polar bears. He and 91±¬ÁĎ glaciologist will field audience questions after of the film, which focuses on the changing Arctic environment.

91±¬ÁĎ News asked Regehr a few questions about his research studying a population of polar bears that traverse the waters between Alaska and Russia.

When do you typically go to Wrangel Island, and how long do you spend there?

I’ve been leading polar bear research on Wrangel Island since 2016. I typically spend about one month there each fall, although the entire trip takes two months because the island is so remote. Unfortunately, everything has been on hold since early 2022 due to the political situation with Russia.

Who are your usual collaborators? What was it like to have a film crew with you?

The research project is a collaboration between the 91±¬ÁĎ, the UNESCO Natural System of Wrangel Island Reserve, the U.S. government, and others. Having a film crew was fun. The only downside was that it meant keeping track of more people, to make sure they didn’t wander off and bump into a bear.

How did you come up with the technique, shown in the film, that uses a wire enclosure to collect polar bear fur for DNA analysis?

A colleague in Alaska developed the first “hair snare” traps for polar bears, and then engineers here at the 91±¬ÁĎ Applied Physics Laboratory improved the design to make the traps lightweight and collapsible. I came up with the secret polar bear sauce (it’s really old fish, old cheese and walrus blubber) that we put inside the traps as a scent attractant.

What do you wish people knew about polar bears?

Actually, I’m constantly amazed by how much the public knows about polar bears — especially kids. It’s great. But if there was one thing I’d emphasize, it’s that polar bears are directly connected to the people that live and work in the Arctic. Climate warming is rapidly changing things for both bears and humans.

Why is important to study polar bears on Wrangel Island?

The U.S. and Russia share a polar bear population, most of which ends up on Wrangel Island each fall to wait for the sea ice to reform. I’ve tagged a bear in Alaska in April, and then stood 10 feet from that same bear on Wrangel Island in October. Polar bears don’t recognize political boundaries, so it’s critical that the U.S. and Russia work together to conserve these awesome animals.

Previously, Regehr also worked on the BBC series , narrated by David Attenborough, where he appears in episode 6. That series is available on Amazon Prime and Google TV.

For more information, contact Regehr at eregehr@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 91±¬ÁĎ’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 91±¬ÁĎ 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 91±¬ÁĎ; 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 91±¬ÁĎ; 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 the past 20 years, the Arctic has lost about one-third of its winter sea ice volume, according to a new study by researchers at the 91±¬ÁĎ and the California Institute of Technology. That decline is largely due to loss of older, multiyear sea ice. New satellite data also show that wintertime Arctic sea ice is likely thinner than previous estimates.

The was published March 10 in Geophysical Research Letters.

“The key takeaway, for me, is the remarkable loss of Arctic winter sea ice volume — one-third of the winter ice volume lost over just 18 years — that accompanied a widely reported loss of old, thick Arctic sea ice, and decline in end-of-summer ice extent,” said co-author , a polar scientist at the 91±¬ÁĎ Applied Physics Laboratory.

Seasonal sea ice, which melts completely each summer rather than accumulating over years, is replacing thicker, multiyear ice. This switch is largely responsible for the sea ice thinning, according to the new research.

“Arctic snow depth, sea ice thickness and volume are three very challenging measurements to obtain,” Kwok remarked.

The newest technology, a combination of ICESat-2 lidar data and CryoSat-2 radar data, is able for the first time to estimate the depth of the snow on top of the Arctic sea ice. Using snow depth and the height of sea ice exposed above water, the study found that multiyear Arctic sea ice lost 16% of its winter volume, or approximately half a meter (about 1.5 feet) of thickness, in the three years since the launch of ICESat-2 in 2018.

“We weren’t really expecting to see this decline, for the ice to be this much thinner in just three short years,” said lead author at CalTech’s Jet Propulsion Laboratory.

Scientists estimate sea ice thickness using snow depth and the height of the floating ice above the sea surface. Snow can weigh ice down, changing how ice floats in the ocean. The new study compared ice thickness using snow depths from satellite radar and lidar to previous observations of ice thickness and snow depth from climate records. The comparisons show that using climatology-based estimates of snow depth can result in overestimating sea ice thickness by up to one-fifth, or as much as 20 centimeters (0.7 feet).

To provide context for sea ice thickness estimates from 2018 to 2021, the study used an 18-year record of sea ice observations spanning the older ICESat records and the newer ICESat-2 and CryoSat-2 satellites to capture monthly changes in Arctic sea ice thickness and volume. The longer 18-year record showed a loss of about 6,000 cubic kilometers (1,400 cubic miles) of winter ice volume, or about one-third, largely driven by the switch from predominantly multiyear ice to thinner, seasonal sea ice.

Older, multiyear ice tends to be thicker and therefore more resistant to melting. As that “reservoir” of old Arctic sea ice declines and seasonal ice becomes the norm, the overall thickness and volume of Arctic sea ice is expected to drop further.

“Current models predict that by the mid-century we can expect ice-free summers in the Arctic, when the older ice, thick enough to survive the melt season is gone,” Kacimi said.

For more information, contact Kwok at rkwok@apl.washington.edu or Kacimi at sahra.kacimi@jpl.nasa.gov

This article was adapted from a by the American Geophysical Union.

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 91±¬ÁĎ 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 91±¬ÁĎ 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 91±¬ÁĎ 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 91±¬ÁĎ; 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.

The ice shelf on Antarctica’s Pine Island Glacier lost about one-fifth of its area from 2017 to 2020, mostly in three dramatic breaks. The timelapse video incorporates satellite images from January 2015 to March 2020. For most of the first two years, the satellite took high-resolution images every 12 days; then for more than three years it captured images of the ice shelf every six days. Images are from the Copernicus Sentinel-1 satellites operated by the European Space Agency on behalf of the European Union.
Credit: Joughin et al./Science Advances

For decades, the ice shelf helping to hold back one of the fastest-moving glaciers in Antarctica has gradually thinned. Analysis of satellite images reveals a more dramatic process in recent years: From 2017 to 2020, large icebergs at the ice shelf’s edge broke off, and the glacier sped up.

Since floating ice shelves help to hold back the larger grounded mass of the glacier, the recent speedup due to the weakening edge could shorten the timeline for Pine Island Glacier’s eventual collapse into the sea. The from researchers at the 91±¬ÁĎ and British Antarctic Survey was published June 11 in the open-access journal Science Advances.

“We may not have the luxury of waiting for slow changes on Pine Island; things could actually go much quicker than expected,” said lead author , a glaciologist at the 91±¬ÁĎ Applied Physics Laboratory. “The processes we’d been studying in this region were leading to an irreversible collapse, but at a fairly measured pace. Things could be much more abrupt if we lose the rest of that ice shelf.”

Pine Island Glacier contains approximately 180 trillion tons of ice — equivalent to 0.5 meters, or 1.6 feet, of global sea level rise. It is already responsible for much of Antarctica’s contribution to sea-level rise, causing about one-sixth of a millimeter of sea level rise each year, or about two-thirds of an inch per century, a rate that’s expected to increase. If it and neighboring Thwaites Glacier speed up and flow completely into the ocean, releasing their hold on the larger West Antarctic Ice Sheet, global seas could rise by several feet over the next few centuries.

These glaciers have attracted attention in recent decades as their ice shelves thinned because warmer ocean currents melted the ice’s underside. From the 1990s to 2009, Pine Island Glacier’s motion toward the sea accelerated from 2.5 kilometers per year to 4 kilometers per year (1.5 miles per year to 2.5 miles per year). The glacier’s speed then stabilized for almost a decade.

Results show that what’s happened more recently is a different process, Joughin said, related to internal forces on the glacier.

From 2017 to 2020, Pine Island’s ice shelf lost one-fifth of its area in a few dramatic breaks that were captured by the Copernicus Sentinel-1 satellites, operated by the European Space Agency on behalf of the European Union. The researchers analyzed images from January 2015 to March 2020 and found that the recent changes on the ice shelf were not caused by processes directly related to ocean melting.

“The ice shelf appears to be ripping itself apart due to the glacier’s acceleration in the past decade or two,” Joughin said.

Two points on the glacier’s surface that were analyzed in the paper sped up by 12% between 2017 and 2020. The authors used an ice flow model developed at 91±¬ÁĎ to confirm that the loss of the ice shelf caused the observed speedup.

“The recent changes in speed are not due to melt-driven thinning; instead they’re due to the loss of the outer part of the ice shelf,” Joughin said. “The glacier’s speedup is not catastrophic at this point. But if the rest of that ice shelf breaks up and goes away then this glacier could speed up quite a lot.”

It’s not clear whether the shelf will continue to crumble. Other factors, like the slope of the land below the glacier’s receding edge, will come into play, Joughin said. But the results change the timeline for when Pine Island’s ice shelf might disappear and how fast the glacier might move, boosting its contribution to rising seas.

“The loss of Pine Island’s ice shelf now looks like it possibly could occur in the next decade or two, as opposed to the melt-driven subsurface change playing out over 100 or more years,” said co-author , an ocean physicist at British Antarctic Survey. “So it’s a potentially much more rapid and abrupt change.”

Pine Island’s shelf is important because it’s helping to hold back this relatively unstable West Antarctic glacier, the way the curved buttresses on Notre Dame cathedral hold up the cathedral’s mass. Once those buttresses are removed, the slow-moving glacier can flow more quickly downward to the ocean, contributing to rising seas.

“Sediment records in front of and beneath the Pine Island ice shelf indicate that the glacier front has remained relatively stable over a few thousand years,” Dutrieux added. “Regular advance and break-ups happened at approximately the same location until 2017, and then successively worsened each year until 2020.”

Other co-authors are and at the 91±¬ÁĎ; and Mark Barham at British Antarctic Survey. The study was funded by the U.S. National Science Foundation, NASA and the U.K. Natural Environment Research Council.

For more information, contact Joughin at ian@apl.washington.edu and Dutrieux at pitr1@bas.ac.uk

NSF: OPP-1643285, NASA grant: NNX17AG54G

Freshwater is accumulating in the Arctic Ocean. The Beaufort Sea, which is the largest Arctic Ocean freshwater reservoir, has increased its freshwater content by 40% over the past two decades. How and where this water will flow into the Atlantic Ocean is important for local and global ocean conditions.

A study from the 91±¬ÁĎ, Los Alamos National Laboratory and the National Oceanic and Atmospheric Administration shows that this freshwater travels through the Canadian Archipelago to reach the Labrador Sea, rather than through the wider marine passageways that connect to seas in Northern Europe. The was published Feb. 23 in Nature Communications.

“The Canadian Archipelago is a major conduit between the Arctic and the North Atlantic,” said lead author , a 91±¬ÁĎ postdoctoral researcher at the Cooperative Institute for Climate, Ocean and Ecosystem Studies. “In the future, if the winds get weaker and the freshwater gets released, there is a potential for this high amount of water to have a big influence in the Labrador Sea region.”

The finding has implications for the Labrador Sea marine environment, since Arctic water tends to be fresher but also rich in nutrients. This pathway also affects larger oceanic currents, namely a conveyor-belt circulation in the Atlantic Ocean in which colder, heavier water sinks in the North Atlantic and comes back along the surface as the Gulf Stream. Fresher, lighter water entering the Labrador Sea could slow that overturning circulation.

“We know that the Arctic Ocean has one of the biggest climate change signals,” said co-author at the 91±¬ÁĎ-based Cooperative Institute for Climate, Ocean and Atmosphere Studies. “Right now this freshwater is still trapped in the Arctic. But once it gets out, it can have a very large impact.”

Fresher water reaches the Arctic Ocean through rain, snow, rivers, inflows from the relatively fresher Pacific Ocean, as well as the recent melting of Arctic Ocean sea ice. Fresher, lighter water floats at the top, and clockwise winds in the Beaufort Sea push that lighter water together to create a dome.

When those winds relax, the dome will flatten and the freshwater gets released into the North Atlantic.

“People have already spent a lot of time studying why the Beaufort Sea freshwater has gotten so high in the past few decades,” said Zhang, who began the work at Los Alamos National Laboratory. “But they rarely care where the freshwater goes, and we think that’s a much more important problem.”

Using a technique Zhang developed to track ocean salinity, the researchers simulated the ocean circulation and followed the Beaufort Sea freshwater’s spread in a past event that occurred from 1983 to 1995.

Their experiment showed that most of the freshwater reached the Labrador Sea through the Canadian Archipelago, a complex set of narrow passages between Canada and Greenland. This region is poorly studied and was thought to be less important for freshwater flow than the much wider Fram Strait, which connects to the Northern European seas.

In the model, the 1983-1995 freshwater release traveled mostly along the North American route and significantly reduced the salinities in the Labrador Sea — a freshening of 0.2 parts per thousand on its shallower western edge, off the coast of Newfoundland and Labrador, and of 0.4 parts per thousand inside the Labrador Current.

The volume of freshwater now in the Beaufort Sea is about twice the size of the case studied, at more than 23,300 cubic kilometers, or more than 5,500 cubic miles. This volume of freshwater released into the North Atlantic could have significant effects. The exact impact is unknown. The study focused on past events, and current research is looking at where today’s freshwater buildup might end up and what changes it could trigger.

“A freshwater release of this size into the subpolar North Atlantic could impact a critical circulation pattern, called the Atlantic Meridional Overturning Circulation, which has a significant influence on Northern Hemisphere climate,” said co-author at Los Alamos National Lab.

This research was funded by the Department of Energy, the National Science Foundation, Los Alamos National Laboratory, and NOAA. Other authors are at the 91±¬ÁĎ Applied Physics Laboratory and and at Los Alamos National Lab.

For more information, contact Zhang at jiaxuzh@uw.edu.

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 91±¬ÁĎ 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 91±¬ÁĎ 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 91±¬ÁĎ; 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

Using the most advanced Earth-observing laser instrument NASA has ever flown in space, a team of scientists led by the 91±¬ÁĎ has made precise measurements of how the Greenland and Antarctic ice sheets have changed over 16 years.

In a published April 30 in the journal Science, researchers found the net loss of ice from Antarctica, along with Greenland’s shrinking ice sheet, has been responsible for 0.55 inches (14 millimeters) of sea level rise to the global ocean since 2003. In Antarctica, sea level rise is being driven by the loss of the floating ice shelves melting in a warming ocean. These ice shelves help hold back the flow of land-based ice.

The findings come from the Ice, Cloud and land Elevation Satellite 2 (ICESat-2), and began taking detailed global elevation measurements, including over Earth’s frozen regions. By comparing the new data with measurements taken by the original ICESat from 2003 to 2009, researchers have generated a comprehensive portrait of the complexities of ice sheet change — and insights into the future of Greenland and Antarctica.

“If you watch a glacier or ice sheet for a month, or a year, you’re not going to learn much about what the climate is doing to it,” said lead author , a glaciologist at the 91±¬ÁĎ Applied Physics Laboratory. “We now have a 16-year span between ICESat and ICESat-2 and can be much more confident that the changes we’re seeing in the ice have to do with the long-term changes in the climate.ĚýAnd ICESat-2 is a really remarkable tool for making these measurements. We’re seeing high-quality measurements that carpet both ice sheets, which let us make a detailed and precise comparison with the ICESat data.”

Previous studies of ice loss or gain often analyze data from multiple satellites and airborne missions. The new study takes a single type of measurement — height as measured by an instrument that bounces laser pulses off the ice surface — providing the most detailed and accurate picture of ice sheet change to date.

The researchers took tracks of ICESat measurements and overlaid the denser tracks of ICESat-2 measurements from 2019. Where the two data sets intersected — tens of millions of sites — they ran the data through computer programs that accounted for the snow density and other factors, and then calculated the mass of ice lost or gained.

“The new analysis reveals the ice sheets’ response to changes in climate with unprecedented detail, revealing clues as to why and how the ice sheets are reacting the way they are,” said co-author , a glaciologist at NASA’s Jet Propulsion Laboratory in Pasadena, California.

The study found that Greenland’s ice sheet lost an average of 200 gigatons of ice per year, and Antarctica’s ice sheet lost an average of 118 gigatons of ice per year. One gigaton of ice is enough to fill 400,000 Olympic-sized swimming pools.

Of the sea level rise that resulted from ice sheet meltwater and iceberg calving, about two-thirds of it came Greenland, the other third from Antarctica, Smith said.

“It was amazing to see how good the ICESat-2 data looked, right out of the gate,” said co-author at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “These first results looking at land ice confirm the consensus from other research groups, but they also let us look at the details of change in individual glaciers and ice shelves at the same time.”

In Greenland, there was a significant amount of thinning of coastal glaciers, Smith said. The Kangerlussuaq and Jakobshavn glaciers, for example, have lost 14 to 20 feet (4 to 6 meters) of elevation per year. Warmer summer temperatures have melted ice from the surface of the glaciers and ice sheets, and in some places warmer ocean water erodes away the ice at their fronts.

In Antarctica, the dense tracks of ICESat-2 measurements showed that the ice sheet is getting thicker in parts of the continent’s interior, likely as a result of increased snowfall, Smith said. But the loss of ice from the continent’s margins, especially in West Antarctica and the Antarctic Peninsula, far outweighs any gains in the interior. In those places, the ocean is also likely to blame.

“In West Antarctica, we’re seeing a lot of glaciers thinning very rapidly,” Smith said. “There are ice shelves at the downstream end of those glaciers, floating on water. And those ice shelves are thinning, letting more ice flow out into the ocean as the warmer water erodes the ice.”

These ice shelves, which rise and fall with the tides, can be difficult to measure, said co-author , a glaciologist at Scripps Institution of Oceanography at the University of California, San Diego. Some of them have rough surfaces, with crevasses and ridges, but the precision and high resolution of ICESat-2 allows researchers to measure overall changes, without worrying about these features skewing the results.

This is one of the first times that researchers have measured loss of the floating ice shelves around Antarctica simultaneously with loss of the continent’s ice sheet.

Ice that melts from ice shelves doesn’t raise sea levels, since it’s already floating — just like an ice cube melting in a full cup of water doesn’t overflow the glass. But the ice shelves do provide stability for the glaciers and ice sheets behind them.

“It’s like an architectural buttress that holds up a cathedral,” Fricker said. “The ice shelves hold the ice sheet up. If you take away the ice shelves, or even if you thin them, you’re reducing that buttressing force, so the grounded ice can flow faster.”

The researchers found ice shelves in West Antarctica, where many of the continent’s fastest-moving glaciers are located, are losing mass. Patterns of thinning show that Thwaites and Crosson ice shelves have thinned the most, an average of about 5 meters (16 feet) and 3 meters (10 feet) of ice per year, respectively.

The study was funded by NASA. Other co-authors are Johan Nilsson and Fernando Paolo at NASA’s Jet Propulsion Laboratory; Brooke Medley, Thorsten Markus and H. Jay Zwally at NASA’s Goddard Space Flight Center; Nicholas Holschuh at Amherst College; Susheel Adusumilli at the University of California, San Diego; Kelly Brunt at the University of Maryland; Bea Csatho at the University of Buffalo; Kaitlin Harbeck at KBR; and Matthew Siegfried at the Colorado School of Mines. Smith and Neumann are both affiliate faculty members in the 91±¬ÁĎ Department of Earth & Space Sciences.

For more information contact Smith at besmith@uw.edu, Fricker at hafricker@ucsd.edu, Gardner at alex.s.gardner@jpl.nasa.gov and Neumann at thomas.neumann@nasa.gov.Ěý

This article is adapted from a NASA .

NASA grants: NNX15AE15G, NNX15AC80G, NNX16AM01G, NNX17AI03G

Polar bears are spending more time on land than they did in the 1990s due to reduced sea ice, new 91±¬ÁĎ-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 91±¬ÁĎ 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 91±¬ÁĎ; 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 °ě±ô˛ąľ±»ĺ°ů±đ°ŞłÜ·É.±đ»ĺłÜĚýor 206-616-9030.

This story is adapted from a .