Amid all the changes in Earth鈥檚 climate, sea ice in the stormy Southern Ocean surrounding Antarctica was, for a long time, an odd exception. The maximum winter sea ice cover remained steady or even increased slightly from the late 1970s through 2015, despite rising global temperatures.

That began to change in 2016. Several years of decline led to , more than five standard deviations below the average from the satellite record. The area of sea ice was 2.2 million square kilometers below the average from the satellite record, a loss almost 12 times the size of Washington state. The most recent winter鈥檚 peak, recorded in September 2024, was to the previous year鈥檚 record low.

天美影视传媒 researchers show that the all-time record low can be explained by warm Southern Ocean conditions and patterns in the winds that circled Antarctica months earlier, allowing forecasts for sea ice coverage around the South Pole to be generated six or more months in advance. This could support regional and global weather and climate models.

The open-access was published Nov. 20 in Nature Communications Earth & Environment.

鈥淪ince 2015, total Antarctic sea ice area has dramatically declined,鈥� said lead author , a UW doctoral student in atmospheric and climate science. 鈥淪tate-of-the-art forecasting methods for sea ice generally struggle to produce reliable forecasts at such long leads. We show that winter Antarctic sea ice has significant predictability at six- to nine-month lead times.鈥�

The authors used a global climate model to simulate how ocean and air temperatures, including longer-term cycles like El Ni帽o and La Ni帽a, affect sea ice in the Southern Ocean.

Results showed that the 2023 El Ni帽o was less important than previously thought. Instead, an arching pattern of regional winds, and their effects on ocean temperatures up to six months in advance, could explain 70% of the 2023 record-low winter sea ice. These winds cause ocean mixing in the Southern Ocean that can pull deeper warm water up to the surface, thus suppressing sea ice growth. Winds can also push sea ice poleward toward Antarctica to prevent the sea ice edge from expanding north, transport heat from lower latitudes toward the poles, and generate ocean waves that break up sea ice.

Using the same approach for the 2024 observations correctly predicted that this would be another low year for Southern Ocean sea ice cover.

鈥淚t鈥檚 interesting that, despite how unusual the winter sea ice conditions were in 2023 and again in 2024, our results show they were remarkably predictable over 6 months in advance,鈥� said co-author , a UW research associate professor of atmospheric and climate science.

Antarctic sea ice is important because it affects marine and coastal ecosystems and interactions between ocean and atmosphere in the Southern Ocean. It also affects global climate by reflecting sunlight in the Southern Hemisphere and influencing ice sheets and global currents.

鈥淎ntarctic sea ice is a major control on the rate of global warming and the stability of ice on the Antarctic continent,鈥� Espinosa said. 鈥淚n fact, the sea ice acts to buttress ice shelves, increasing their stability and slowing the rate of global sea level rise. This ice is also important for marine and coastal ecosystems.鈥�

As summer arrives in the Southern Hemisphere, the remains sparse around Antarctica, close to a record low for this time of the year.

鈥淥ur success at predicting these major sea ice loss events so far in advance demonstrates our understanding of the mechanism that caused them,鈥� said co-author , a UW professor of atmospheric and climate science. 鈥淥ur model and methods are geared up to predict future sea ice loss events.鈥�

The research was funded by the National Science Foundation and the U.S. Department of Energy.

For more information, contact Espinosa at zespinosa97@gmail.com, Bitz at bitz@uw.edu and Blanchard-Wrigglesworth at edwardbw@uw.edu.

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 天美影视传媒 was published Oct. 22 in the journal Ecology. It鈥檚 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鈥搕haw cycles could be causing ice buildup and injuries.

鈥淚n addition to the anticipated responses to climate change for polar bears, there are going to be other, unexpected responses,鈥� said lead author , a senior principal scientist at the UW Applied Physics Laboratory and a professor in the UW School of Aquatic and Fishery sciences. 鈥淎s 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鈥� paws.鈥�

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.

鈥淚’d never seen that before,鈥� Laidre said. 鈥淭he two most-affected bears couldn’t run 鈥� 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.鈥�

Researchers have studied these two polar bear populations since the 1990s but haven鈥檛 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鈥� paws 鈥� 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 鈥溾�� 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鈥� feet and then refreeze to form ice. Also, unlike other areas, polar bears living at glaciers鈥� 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.

鈥淲e鈥檝e seen these icing-related injuries on individual polar bears,鈥� Laidre said. 鈥淏ut I would hesitate to jump to conclusions about how this might affect them at a population level. We really don鈥檛 know.鈥�

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

鈥淭he surface of Arctic sea ice is transforming with climate change,鈥� Webster said. 鈥淭he 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.鈥�

Asked what can be done to help the polar bears, Laidre had a simple response: 鈥淲e can reduce greenhouse gas emissions and try to limit climate warming.鈥�

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.

There鈥檚 enough water frozen in Greenland and Antarctic glaciers that if they melted, global seas would rise by many feet. What will happen to these glaciers over the coming decades is the biggest unknown in the future of rising seas, partly because glacier fracture physics is not yet fully understood.

A critical question is how warmer oceans might cause glaciers to break apart more quickly. 天美影视传媒 researchers have demonstrated the fastest-known large-scale breakage along an Antarctic ice shelf. The , recently published in AGU Advances, shows that a 6.5-mile (10.5 kilometer) crack formed in 2012 on Pine Island Glacier 鈥� a retreating ice shelf that holds back the larger West Antarctic ice sheet 鈥� in about 5 and a half minutes. That means the rift opened at about 115 feet (35 meters) per second, or about 80 miles per hour.

鈥淭his is to our knowledge the fastest rift-opening event that’s ever been observed,鈥� said lead author , who did the work as part of her doctoral research at the UW and Harvard University and is now a postdoctoral researcher at Stanford University. 鈥淭his shows that under certain circumstances, an ice shelf can shatter. It tells us we need to look out for this type of behavior in the future, and it informs how we might go about describing these fractures in large-scale ice sheet models.鈥�

A rift is a crack that passes all the way through the roughly 1,000 feet (300 meters) of floating ice for a typical Antarctic ice shelf. These cracks are the precursor to ice shelf calving, in which large chunks of ice break off a glacier and fall into the sea. Such events happen often at Pine Island Glacier 鈥� the iceberg observed in the study has long since separated from the continent.

鈥淚ce shelves exert a really important stabilizing influence on the rest of the Antarctic ice sheet. If an ice shelf breaks up, the glacier ice behind really speeds up,鈥� Olinger said. 鈥淭his rifting process is essentially how Antarctic ice shelves calve large icebergs.鈥�

In other parts of Antarctica, rifts often develop over months or years. But it can happen more quickly in a fast-evolving landscape like Pine Island Glacier, where researchers believe the West Antarctic Ice Sheet has already passed a tipping point on its collapse into the ocean.

Satellite images provide ongoing observations. But orbiting satellites pass by each point on Earth only every three days. What happens during those three days is harder to pin down, especially in the dangerous landscape of a fragile Antarctic ice shelf.

For the new study, the researchers combined tools to understand the rift鈥檚 formation. They used seismic data recorded by instruments placed on the ice shelf by other researchers in 2012 with radar observations from satellites.

Glacier ice acts like a solid on short timescales, but it鈥檚 more like a viscous liquid on long timescales.

鈥淚s rift formation more like glass breaking or like Silly Putty being pulled apart? That was the question,鈥� Olinger said. 鈥淥ur calculations for this event show that it鈥檚 a lot more like glass breaking.鈥�

If the ice were a simple brittle material, it should have shattered even faster, Olinger said. Further investigation pointed to the role of seawater. Seawater in the rifts holds the space open against the inward forces of the glacier. And since seawater has viscosity, surface tension and mass, it can鈥檛 just instantly fill the void. Instead, the pace at which seawater fills the opening crack helps slow the rift鈥檚 spread.

鈥淏efore we can improve the performance of large-scale ice sheet models and projections of future sea-level rise, we have to have a good, physics-based understanding of the many different processes that influence ice shelf stability,鈥� Olinger said.

The research was funded by the National Science Foundation. Co-authors are and , both UW faculty members in Earth and space sciences who began advising the work while at Harvard University.

For more information, contact Olinger at solinger@stanford.edu.

In the frigid waters surrounding Antarctica, an unusual seasonal cycle occurs. During winter, from March to October, the sun barely rises. As seawater freezes it rejects salts, creating pockets of extra-salty brine where microbes live in winter. In summer, the sea ice melts under constant daylight, producing warmer, fresher water at the surface.

This remote ecosystem is home to much of the Southern Ocean鈥檚 photosynthetic life. A new 天美影视传媒 study provides the first measurements of how sea-ice algae and other single-celled life adjust to these seasonal rhythms, offering clues to what might happen as this environment shifts under climate change.

The , published Sept. 15 in the International Society for Microbial Ecology鈥檚 ISME Journal, contains some of the first measurements of how sea-ice microbes respond to changing conditions.

鈥淲e know very little about how sea-ice microbes respond to changes in salinity and temperature,鈥� said lead author , a UW postdoctoral researcher who did the work while pursuing her doctorate in oceanography at the UW. 鈥淎nd until now we knew almost nothing about the molecules they produce and use in chemical reactions to stay alive, which are important for supporting higher organisms in the ecosystem as well as for climate impacts, like carbon storage and cloud formation.鈥�

The polar oceans play an important role in global ocean currents and in supporting marine ecosystems. Microbes form the base of the food web, supporting larger life forms.

鈥淧olar oceans make up a significant portion of the world鈥檚 oceans, and these are very productive waters,鈥� said senior author , a UW assistant professor of oceanography. 鈥淭hese waters support big swarms of krill, the whales that come to feed on those krill, and either polar bears or penguins. And the start of that whole ecosystem are these single-celled microscopic algae. We just know so little about them.鈥�

The tiny organisms are also important for the climate, since they quietly perform photosynthesis and soak up carbon from the atmosphere. Polar algae are especially good at producing sulfur-containing molecules that give beaches their distinctive smell and, when lofted into the air in sea spray, promote formation of clouds that can reduce penetration of solar rays.

Antarctic sea ice, though long stable, is at an this year.

In other oceans, satellite instruments can capture dramatic seasonal phytoplankton blooms from space 鈥� but that isn鈥檛 possible for microbes hidden under sea ice. And Antarctic waters are particularly challenging to visit, leaving researchers with almost no measurements in winter.

In late 2018, Dawson and co-author traveled to , a U.S. research station on the West Antarctic Peninsula. They used a small boat to sample seawater and sea ice at the same nearby sites every three days.

Back on shore, the two graduate students performed 10-day experiments in tanks to see which microbes grew as temperature and salinity were adjusted to mimic sea-ice formation and melt. They also shipped samples back to Seattle for more complex measurements of the samples鈥� genetics and metabolites, the small organic molecules produced by the cell.

Results revealed how single-celled algae deal with their fluctuating environments. As temperatures drop, the cells produce cryoprotectants, similar to antifreeze, to prevent their cellular fluid from crystallizing. Many of the most common cryoprotectant molecules were the same across different microbial lifeforms.

As salinity changes, to avoid either bursting in freshening waters or becoming desiccated like raisins in salty conditions, the cells change the concentration of salt-like organic molecules. Many such molecules serve a dual role as cryoprotectants, to balance conditions inside and outside the cell to maintain water balance.

The results show that under short-term temperature and salinity changes, community structure in each sample remained stable while adjusting the production of protective molecules. Different microbe species showed consistent responses to changing conditions. This should simplify modeling future responses to climate change, Young said.

Results also hint that the production of omega-3 fatty acids may decline in lower-salinity environments. This would be bad news for consumers of krill oil supplements, and for the marine ecosystem that relies on those algae-derived nutrients. Future research now underway by the UW group aims to confirm that result 鈥� especially with the prospect of increasing freshwater input from melting sea ice and glaciers.

鈥淲e鈥檙e interested in how these sea-ice algae contend with changes in temperature, salinity and light under normal conditions,鈥� Dawson said. 鈥淏ut then we also have climate change, which is completely remodeling the landscape in terms of when sea ice is forming, how much sea ice forms, how long it stays before it melts, as well as the quantity of freshwater input from glaciers. So we’re both trying to capture what’s happening now, and also asking how that can inform what might happen in the future.鈥�

The study was funded by the National Science Foundation, the Simons Foundation, and the Alfred P. Sloan Foundation. Other co-authors are Anitra Ingalls, Jody Deming, Joshua Sacks and Laura Carlson at the UW; Natalia Erazo, Elizabeth Connors and Jeff Bowman at Scripps Institution of Oceanography; and Veronica Mierzejewski at Arizona State University.

For more information, contact Dawson at hmdawson@uw.edu or Young at youngjn@uw.edu.

New research from the 天美影视传媒 and Polar Bears International in Bozeman, Montana, quantifies the relationship between greenhouse gas emissions and the survival of polar bear populations. The , published online Aug. 31 in Science, combines past research and new analysis to provide a quantitative link between greenhouse gas emissions and polar bear survival rates.

A warming Arctic is limiting polar bears鈥� access to sea ice, which the bears use as a hunting platform. In ice-free summer months the bears must fast. While in a worst-case scenario the adult bears will die, before then they will lose the ability to successfully raise cubs.

鈥淯ntil now, scientists hadn鈥檛 offered the quantitative evidence to relate greenhouse gas emissions to population decline,鈥� said second author , a UW professor of atmospheric sciences.

Bitz did data analysis for the new report that shows a direct link between cumulative greenhouse gas emissions and polar bear demographic changes. The link largely explains recent declining trends in some polar bear subpopulations, such as in western Hudson Bay. The paper also has policy implications because it allows a formal assessment of how future proposed actions would impact polar bears.

鈥淚 hope the U.S. government fulfills its legal obligation to protect polar bears by limiting greenhouse gas emissions from human activity,鈥� Bitz said. 鈥淚 hope investments are made into fossil fuel alternatives that exist today, and to discover new technologies that avoid greenhouse gas emissions.鈥�

In 2008, polar bears became the first species listed under the Endangered Species Act because of the threat of climate change. The biological link between warming and polar bear survival was clear, and scientists projected that up to two-thirds of the world鈥檚 polar bears could disappear by mid-century.

The Endangered Species Act requires that any government-authorized projects, including oil and gas leases, do not further endanger any listed species. But a document released by the U.S. Department of the Interior in 2008, known as the , required specific proof of how a proposed project鈥檚 greenhouse gas emissions would affect a species鈥� survival before the ESA could be fully implemented for species threatened by climate change.

鈥淲e鈥檝e known for decades that continued warming and sea ice loss ultimately can only result in reduced distribution and abundance of polar bears,鈥� said lead author , chief scientist emeritus at Polar Bears International and adjunct professor at the University of Wyoming. 鈥淯ntil now, we鈥檝e lacked the ability to distinguish impacts of greenhouse gases emitted by particular activities from the impacts of historic cumulative emissions. In this paper, we reveal a direct link between anthropogenic greenhouse gas emissions and cub survival rates.鈥�

The new paper, published in the 50th anniversary year of the Endangered Species Act and the 15-year anniversary of the listing of polar bears, brings new science to fill that knowledge gap.

Advances in climate science mean that precise links can now be established between emissions and species survival. Bitz was second author on a , connecting polar bear fasting to ice-free days and calculating the annual fasting limits that lead to mortality. That study considered not just adult polar bear鈥檚 survival, but also its recruitment success, meaning its ability to have cubs and raise them to the age of independence.

The new paper links ice-free days and polar bear fasting limits to cumulative greenhouse gas emissions. It finds that, for example, the hundreds of power plants in the U.S. will emit more than 60 gigatons of greenhouse gas emissions over their 30-year lifespans, which would reduce polar bear cub survival in the southern Beaufort Sea population by about 4%.

鈥淥vercoming the challenge of the Bernhardt Opinion is absolutely in the realm of climate research,鈥� Bitz said. 鈥淲hen the memo was written in 2008, we could not say how human-generated greenhouse gas emissions equated to a decline in polar bear populations. But within a few years we could directly relate the quantity of emissions to climate warming and later to Arctic sea ice loss as well. Our study shows that not only sea ice, but polar bear survival, can be directly related to our greenhouse gas emissions.鈥�

The study has implications beyond polar bears and sea ice, authors say. The same method of analysis can be adapted for other species and species habitat with direct connections to global warming, such as coral reefs, the endangered that reside in the Florida keys, or beach-nesting species that are affected by rising sea levels.

鈥淧olar bears are beautiful creatures, and I hope they survive global warming. However, the health and well-being of humans, especially the most vulnerable, is of the utmost importance,鈥� Bitz said. 鈥淎ll of us have experienced heat extremes in the last few years. The harm is inescapable.

鈥淓verything governments and industries can do to reduce greenhouse gas emissions matters, and will help avoid the worst consequences. I鈥檓 excited to see the innovative proposals for the Inflation Reduction Act 鈥� I hope they stimulate the healthier future that polar bears, and all of us, need.鈥�

The study was funded by Polar Bears International and the National Science Foundation.

For more information, contact Bitz at bitz@uw.edu and Amstrup at samstrup@pbears.org

Note: This was adapted from a Polar Bears International .

, a researcher at the UW 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 UW glaciologist will field audience questions after of the film, which focuses on the changing Arctic environment.

UW 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鈥檝e 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 天美影视传媒, 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鈥檛 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 鈥渉air snare鈥� traps for polar bears, and then engineers here at the UW Applied Physics Laboratory improved the design to make the traps lightweight and collapsible. I came up with the secret polar bear sauce (it鈥檚 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鈥檓 constantly amazed by how much the public knows about polar bears 鈥� especially kids. It鈥檚 great. But if there was one thing I鈥檇 emphasize, it鈥檚 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鈥檝e tagged a bear in Alaska in April, and then stood 10 feet from that same bear on Wrangel Island in October. Polar bears don鈥檛 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.

An international team of researchers has combined satellite imagery and climate and ocean records to obtain the most detailed understanding yet of how the West Antarctic Ice Sheet 鈥� which contains enough ice to raise global sea level by 11 feet, or 3.3 meters 鈥� is responding to climate change.

The researchers, from the 天美影视传媒, the University of Cambridge and the University of Edinburgh, found that the pace and extent of ice destabilization along West Antarctica鈥檚 coast varies according to differences in regional climate.

The , published Jan. 16 in Nature Communications, shows that while the West Antarctic Ice Sheet continues to retreat, the pace of retreat slowed in a key region between 2003 and 2015. This slowdown was driven by ocean temperatures, which were in turn caused by variations in offshore winds.

The marine-based West Antarctic Ice Sheet, home to the vast and unstable Pine Island and Thwaites glaciers, sits on an underwater landmass peaking聽 1.5 miles, or 2.5 kilometers, below the ocean鈥檚 surface. Since the early 1990s, scientists have observed an abrupt acceleration in ice melt, retreat and speed in this area, which is attributed in part to human-induced climate change over the past century.

Previous studies, including from the UW, indicated that the observed changes could be the onset of an irreversible, ice-sheet-wide collapse, which would continue independently of any further climate-driven influence.

鈥淭he idea that once a marine-based ice sheet passes a certain tipping point it will cause a runaway response has been widely reported,鈥� said lead author Frazer Christie at Cambridge University. 鈥淒espite this, questions remain about the extent to which ongoing changes in climate still regulate ice losses along the entire West Antarctic coastline.鈥�

Using observations collected by an array of satellites, the new study found pronounced regional variations in how the West Antarctic Ice Sheet has changed since 2003 due to climate change, with the pace of retreat in the Amundsen Sea Sector, an area of West Antarctica facing the Pacific Ocean, having slowed significantly. That鈥檚 in contrast to the neighboring Bellingshausen Sea Sector, closer to the tip of the Antarctic Peninsula, where glacier retreat accelerated during that time.

By analyzing climate and ocean records, the researchers linked these regional differences to changes in the strength and direction of offshore surface winds. When the prevailing westerly winds are stronger, more of the deeper, warmer ocean water reaches the surface and increases the rate of ice melt.

Winds near the Amundsen Sector slackened between 2003 and 2015, researchers found, because of a deepening of the pressure system. This system is the key atmospheric circulation pattern in the region, and its center 鈥� near which changes in offshore wind strength are greatest 鈥� typically sits offshore of its namesake coast for most of the year.

Researchers found that the accelerated response of the glaciers flowing from the Bellingshausen Sea Sector can be explained by more constant winds there, causing more persistent ocean-driven melt.

Ultimately, the study illustrates the complexity of the competing ice, ocean and atmosphere interactions driving shorter-term changes across West Antarctica, and raises important questions about how quickly the icy continent will evolve in a warming world.

鈥淥cean and atmospheric forcing mechanisms still really, really matter in West Antarctica,鈥� said co-author , a UW professor of Earth and space sciences. 鈥淭hat means that ice-sheet collapse is not inevitable. It depends on how climate changes over the next few decades, which we could influence in a positive way by reducing greenhouse gas emissions.鈥�

And while the strength of the low-pressure cell in the Amundsen Sea is not necessarily tied to levels of greenhouse gases 鈥� itself an active area of study 鈥� the system鈥檚 influence shows that even the West Antarctic Ice Sheet is sensitive to weather and climate shifts.

Results show that changes in ocean, driven by changes in the winds, can slow down and even reverse the loss of ice, Steig says. But he points out that the effect is local and unlikely to last for more than a few decades.

“Only the most aggressive reductions in greenhouse gas emissions can plausibly turn the situation around in the long term,” Steig said.

Other co-authors are Noel Gourmelen and Simon Tett at the University of Edinburgh. The study was supported by the Carnegie Trust for the Universities of Scotland; the Scottish Alliance for Geoscience, Environment and Society; the Prince Albert II of Monaco Foundation; the U.K. Natural Environment Research Council; the U.S. National Science Foundation; the joint U.K./U.S. International Thwaites Glacier Collaboration project; and the European Space Agency.

Adapted from a University of Cambridge . For more information, contact Steig at steig@uw.edu

A warming climate is causing a decline in sea ice in the Arctic Ocean, where loss of sea ice has important ecological, economic and climate impacts. On top of this long-term shift due to climate change are weather events that affect the sea ice from week to week.

The strongest Arctic cyclone ever observed poleward of 70 degrees north latitude struck in January 2022 northeast of Greenland. A new analysis led by the 天美影视传媒 shows that while weather forecasts accurately predicted the storm, ice models seriously underestimated its impact on the region鈥檚 sea ice.

The , published in October in the Journal of Geophysical Research鈥揂tmospheres, suggests that existing models underestimate the impact of big waves on ice floes in the Arctic Ocean.

鈥淭he loss of sea ice in six days was the biggest change we could find in the historical observations since 1979, and the area of ice lost was 30% greater than the previous record,鈥� said lead author , a research assistant professor of atmospheric sciences at the UW. 鈥淭he ice models did predict some loss, but only about half of what we saw in the real world.鈥�

Accurate sea ice forecasts are important safety tools for Northern communities, mariners and others operating in Arctic waters. The accuracy of forecasts in the Arctic Ocean also has broader effects.

鈥淭he skill of a weather forecast in the Arctic affects the skill of weather forecasts in other places,鈥� Blanchard-Wrigglesworth said.

The January 2022 cyclone had the lowest pressure center estimated since satellite records began in 1979 above 70 degrees north. It was an extreme version of a typical winter storm. Climate change doesn鈥檛 appear responsible for the cyclone: The researchers didn鈥檛 find a trend in the strength of intense Arctic cyclones since 1979, and sea ice area was close to the historical normal for that region before the storm hit.

Waves travel through sea ice in the Arctic Ocean, as seen from a ship in October 2015. Credit: Ed Blanchard-Wrigglesworth/天美影视传媒

During the storm, record winds howled over the Arctic Ocean. The waves grew to 8 meters (26 feet) tall in open water and remained surprisingly strong as they traveled through the sea ice. The ice heaved 2 meters (6 feet) up and down near the edge of the pack, and NASA鈥檚 ICESat-2 satellite shows that the waves reached as far as 100 kilometers (60 miles) toward the center of the ice pack.

Six days after the storm struck, the sea ice had thinned significantly in the affected waters north of Norway and Russia, in places losing more than half a meter (about 1.5 feet) of thickness.

鈥淚t was a monster storm, and the sea ice got pummeled. And the sea ice models didn鈥檛 predict that loss, which suggests there are ways we could improve the model physics,鈥� said second author , a research assistant professor at the University of Alaska Fairbanks. She begins a research position at the UW Applied Physics Laboratory in the new year.

The new analysis shows that the atmospheric heat from the storm had a small effect, meaning some other mechanism was to blame for the ice loss. Possibilities, Blanchard-Wrigglesworth suggests, include sea ice that was thinner before the storm hit than models had estimated; that the storm鈥檚 waves broke up ice floes more forcefully than models predicted as they penetrated deep into the ice pack; or that waves churned up deeper, warmer water and brought it into contact with the sea ice, melting the ice from below.

The unexpected ice loss, despite an accurate storm forecast, suggests that this is an area where models could improve. The researchers hope to monitor future storms to pinpoint exactly what led to the dramatic sea ice loss, potentially by placing sensors in the path of a future approaching storm.

While this storm doesn鈥檛 appear to be linked to climate change, the increase of open water as sea ice melts is allowing for larger waves that are eroding Arctic coastlines. Those waves, researchers said, could also affect the remaining sea ice pack.

鈥淕oing into the future, this is something to keep in mind, that these extreme events might produce these episodes of huge sea ice loss,鈥� Blanchard-Wrigglesworth said.

Other co-authors are at NASA, at NASA and the University of Maryland and at the University of Auckland and Brown University. The research was funded by NASA, the U.S. Navy鈥檚 Office of Naval Research and Schmidt Futures.

For more information, contact Blanchard-Wrigglesworth at ed@atmos.uw.edu or Webster at mwebster3@alaska.edu.

Grants: NASA: 80NSSC20K0922, 80NSSC20K0959, ONR-DRI: N00014-21-1-2490

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鈥檚 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.

鈥淲e wanted to survey this region because we didn鈥檛 know much about the polar bears in Southeast Greenland, but we never expected to find a new subpopulation living there,鈥� said lead author , a polar scientist at the 天美影视传媒鈥檚 Applied Physics Laboratory. 鈥淲e knew there were some bears in the area from historical records and Indigenous knowledge. We just didn鈥檛 know how special they were.鈥�

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鈥檚 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.

鈥淧olar 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,鈥� said Laidre, who is also a UW associate professor of aquatic and fishery sciences. 鈥淏ut 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.鈥�

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.

鈥淭hey are the most genetically isolated population of polar bears anywhere on the planet,鈥� said co-author , a professor and geneticist at the University of California, Santa Cruz and investigator at the Howard Hughes Medical Institute. 鈥淲e 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.鈥�

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.

鈥淚n a sense, these bears provide a glimpse into how Greenland鈥檚 bears may fare under future climate scenarios,鈥� Laidre said. 鈥淭he sea ice conditions in Southeast Greenland today resemble what鈥檚 predicted for Northeast Greenland by late this century.鈥�

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鈥檚 roughly 26,000 polar bears use to hunt seals. But polar bears can鈥檛 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.

鈥淭he marine-terminating glaciers in Southeast Greenland are a fairly unique environment,鈥� said co-author , deputy lead scientist at the National Snow and Ice Data Center. 鈥淭hese 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.鈥�

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 鈥� places where some polar bears could survive as sea ice on the ocean鈥檚 surface declines. Similar habitats exist at marine-terminating glaciers on other parts of Greenland鈥檚 coast and the island of Svalbard, a Norwegian territory located east of Greenland.

鈥淓ven 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,鈥� 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.

鈥淚f you鈥檙e concerned about preserving the species, then yes, our findings are hopeful 鈥� I think they show us how some polar bears might persist under climate change,鈥� Laidre said. 鈥淏ut I don鈥檛 think glacier habitat is going to support huge numbers of polar bears. There鈥檚 just not enough of it. We still expect to see large declines in polar bears across the Arctic under climate change.鈥�

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.

鈥淧reserving the genetic diversity of polar bears is crucial going forward under climate change,鈥� Laidre said. 鈥淥fficially recognizing these bears as a separate population will be important for conservation and management.鈥�

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 the Southern Hemisphere, the ice cover around Antarctica gradually expands from March to October each year. During this time the total ice area increases by 6 times to become larger than Russia. The sea ice then retreats at a faster pace, most dramatically around December, when Antarctica experiences constant daylight.

New research led by the 天美影视传媒 explains why the ice retreats so quickly: Unlike other aspects of its behavior, Antarctic sea ice is just following simple rules of physics.

The was published March 28 in Nature Geoscience.

鈥淚n spite of the puzzling longer-term trends and the large year-to-year variations in Antarctic sea ice, the seasonal cycle is really consistent, always showing this fast retreat relative to slow growth,鈥� said lead author , who conducted the study as a postdoctoral researcher at the UW and is now a research scientist at NASA and Columbia University. 鈥淕iven how complex our climate system is, I was surprised that the rapid seasonal retreat of Antarctic sea ice could be explained with such a simple mechanism.鈥�

Previous studies explored whether or warm ocean waters might be responsible for the asymmetry in Antarctica鈥檚 seasonal sea ice cycle. But the new study shows that, just like a hot summer day reaches its maximum sizzling conditions in late afternoon, an Antarctic summer hits peak melting power in midsummer, accelerating warming and sea ice loss, with slower changes in temperature and sea ice when solar input is low during the rest of the year.

The researchers investigated global climate models and found they reproduced the quicker retreat of Antarctic sea ice. They then built a simple physics-based model to show that the reason is the seasonal pattern of incoming solar radiation.

Near the North Pole, Arctic ice cover has gradually decreased since the 1970s with global warming. Antarctic ice cover, however, has seesawed over recent decades. Researchers are still working to understand sea ice around the South Pole and better represent it in climate models.

鈥淚 think because we usually expect Antarctic sea ice to be puzzling, previous studies assumed that the rapid seasonal retreat of Antarctic sea ice was also unexpected 鈥� in contrast to the Arctic, where the seasons of ice advance and retreat are more similar,鈥� Roach said. 鈥淥ur results show that the seasonal cycle in Antarctic sea ice can be explained using very simple physics. In terms of the seasonal cycle, Antarctic sea ice is behaving as we should expect, and it is the Arctic seasonal cycle that is more mysterious.鈥�

The researchers are now exploring why Arctic sea ice doesn鈥檛 follow this pattern, instead each year growing slightly faster over the Arctic Ocean than it retreats. Because Antarctica鈥檚 geography is simple, with a polar continent surrounded by ocean, this aspect of its sea ice may be more straightforward, Roach said.

鈥淲e know the Southern Ocean plays an important role in Earth鈥檚 climate. Being able to explain this key feature of Antarctic sea ice that standard textbooks have had wrong, and showing that the models are reproducing it correctly, is a step toward understanding this system and predicting future changes,鈥� said co-author , a UW professor of atmospheric sciences.

Other co-authors are , a UW research assistant professor in atmospheric sciences; Ian Eisenman at Scripps Institution of Oceanography; and Till Wagner at the University of Wisconsin-Madison. Roach is currently a research scientist with the NASA Goddard Institute for Space Studies. This work was funded by the National Science Foundation, the National Oceanic and Atmospheric Administration and the U.K.-based Scientific Committee on Antarctic Research.

For more information, contact Roach at l.roach@columbia.edu.