Amid all the changes in Earth’s 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’s peak, recorded in September 2024, was to the previous year’s record low.

91̽�� 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.

“Since 2015, total Antarctic sea ice area has dramatically declined,” said lead author , a 91̽��doctoral student in atmospheric and climate science. “State-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.”

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

Results showed that the 2023 El Niño 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.

“It’s 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,” said co-author , a 91̽��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.

“Antarctic sea ice is a major control on the rate of global warming and the stability of ice on the Antarctic continent,” Espinosa said. “In 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.”

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

“Our success at predicting these major sea ice loss events so far in advance demonstrates our understanding of the mechanism that caused them,” said co-author , a 91̽��professor of atmospheric and climate science. “Our model and methods are geared up to predict future sea ice loss events.”

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.

New research from the 91̽�� 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’ 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.

“Until now, scientists hadn’t offered the quantitative evidence to relate greenhouse gas emissions to population decline,” said second author , a 91̽��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.

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

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’s 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’s greenhouse gas emissions would affect a species’ survival before the ESA could be fully implemented for species threatened by climate change.

“We’ve known for decades that continued warming and sea ice loss ultimately can only result in reduced distribution and abundance of polar bears,” said lead author , chief scientist emeritus at Polar Bears International and adjunct professor at the University of Wyoming. “Until now, we’ve 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.”

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’s 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%.

“Overcoming the challenge of the Bernhardt Opinion is absolutely in the realm of climate research,” Bitz said. “When 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.”

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.

“Polar 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,” Bitz said. “All of us have experienced heat extremes in the last few years. The harm is inescapable.

“Everything governments and industries can do to reduce greenhouse gas emissions matters, and will help avoid the worst consequences. I’m excited to see the innovative proposals for the Inflation Reduction Act — I hope they stimulate the healthier future that polar bears, and all of us, need.”

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 .

is a 91̽��-wide institute connecting scholars with community partners to address environmental challenges. The institute announced awards for its 2020 on May 5.

Four research teams were chosen from 43 that applied. Proposals were reviewed by an 11-member committee including faculty and staff in several areas as well as an outside community member. This is the program’s second year.

Each team will receive up to $75,000 as well as administrative and communications support for a 16-month period ending in September 2021.

Crucially, the researchers also plan to collaborate with community partners from El Centro de la Raza locally to universities internationally for these projects. All of the community partners involved are listed on the .

Does vegetation help mitigate roadway and aircraft-related air pollution in Seattle?

, associate professor of environmental and occupational health sciences, is principal investigator on this community-engaged study using drones for 3D air quality measurements.

Co-investigators are professor and assistant professor of civil and environmental engineering, and , professor of atmospheric sciences.

According to their proposal, “Findings from this study will provide local and highly relevant evidence on the effectiveness of urban planning initiatives that may utilize greenery as an approach to address particulate air pollution.”

Hazard planning, food sovereignty and climate adaptation in the Alaskan Arctic��

, assistant professor in the Department of American Indian Studies and the School of Marine and Environmental Affairs, is this project’s principal investigator and co-director.

is a 500-person community in Northwest Alaska about 80 miles above the Arctic Circle. Sea-ice cover around this area has decreased dramatically in the last two decades, increasing coastal erosion during storms and the frequency of traveler distress calls, among other concerns.

For this research, an interdisciplinary team of 91̽��polar researchers will work with area search and rescue volunteers to help Kivalina and its residents achieve more safety, resilience and food sovereignty, and become a model of community-driven polar research. The team also plans to develop new methods in sea ice forecasting to support local decision-making, among several other goals.

Other 91̽��researchers involved are , chair and professor; and , research assistant professor, both in atmospheric sciences.

Píkyav on the Mid-Klamath River: Peeshkêesh Yáv Umúsaheesh

The flows through parts of Oregon and Northern California. Four hydroelectric dams along the river are scheduled for removal in 2022. The , in that area, is among the largest in California.

This research team proposes a river restoration process on the Klamath that centers on Karuk tribal sovereignty using a model of justice, helping to bring tribal perspectives to large-scale governance. The title of the project, they write, translates to “the river will look good” — and the phrase “goes far below the surface to include function, connection and ceremonial renewal.”

The team plans an intergenerational, field-based school on the river, working with Karuk youth and cultural practitioners to gather historical maps, stories and spatial data on Karuk uses of floodplain ecosystems.

91̽��team members for this project are , assistant professor in the School of Marine and Environmental Affairs; , a lecturer in Comparative History of Ideas and the Program on the Environment; and Karuk tribal member Kimberly Yazzie, a doctoral student in the School of Aquatic and Fishery Sciences.

Lessons from urban indigenous immigrants ��

“This project will compare a self-managed indigenous immigrant community still using traditional practices in Iquitos, Peru,” the team wrote, “to a similar indigenous immigrant community nearby that developed with social and political pressures to colonially urbanize and leave traditional practices behind.”

91̽��members of the research team are , affiliate assistant professor of landscape architecture; , photographer with the 91̽��Center for One Health Research; , lecturer in the 91̽��Bothell School of Interdisciplinary Arts & Sciences; Kathleen Wolf, research social scientist with the School of Environment and Forest Sciences; and doctoral student of the School of Public Health.

“We use an innovative, mixed-methods approach by combining indigenous knowledge, science and art to document environmental conditions, ecosystem health, traditional knowledge practices, and human-nature connections in each community,” the team wrote.

Environmental and human health impacts of a new invasive species in Madagascar

A fifth project was in March, representing the second project funded in collaboration with the 91̽��Population Health Initiative. The project’s 91̽��leads are , assistant professor in the School of Aquatic and Fishery Sciences; and , professor in the Department of Environmental and Occupational Health Sciences.

For more information, contact the EarthLab Innovation Grants program lead at elgrants@uw.edu.

91̽�� astrobiologist has created software that simulates multiple aspects of planetary evolution across billions of years, with an eye toward finding and studying potentially habitable worlds.

Barnes, a 91̽��assistant professor of astrobiology, astronomy and data science, released the first version of VPLanet, his virtual planet simulator, in August. He and his co-authors described it in a accepted for publication in the Publications of the Astronomical Society of the Pacific.

“It links different physical processes together in a coherent manner,” he said, “so that effects or phenomena that occur in some part of a planetary system are tracked throughout the entire system. And ultimately the hope is, of course, to determine if a planet is able to support life or not.”

VPLanet’s mission is three-fold, Barnes and co-authors write. The software can:

• simulate newly discovered exoplanets to assess their potential to possess surface liquid water, which is a key to life on Earth and indicates the world is a viable target in the search for life beyond Earth
• model diverse planetary and star systems regardless of potential habitability, to learn about their properties and history, and
• enable transparent and open science that contributes to the search for life in the universe

The first version includes modules for the internal and magnetic evolution of terrestrial planets, climate, atmospheric escape, tidal forces, orbital evolution, rotational effects, stellar evolution, planets orbiting binary stars and the gravitational perturbations from passing stars.

It’s designed for easy growth. Fellow researchers can write new physical modules “and almost plug and play them right in,” Barnes said. VPLanet can also be used to complement more sophisticated tools such as machine learning algorithms.

An important part of the process, he said, is validation, or checking physics models against actual previous observations or past results, to confirm that they are working properly as the system expands.

“Then we basically connect the modules in a central area in the code that can model all members of a planetary system for its entire history,” Barnes said.

And though the search for potentially habitable planets is of central importance, VPLanet can be used for more general inquiries about planetary systems.

“We observe planets today, but they are billions of years old,” he said. This is a tool that allows us to ask: ‘How do various properties of a planetary system evolve over time?’”

The project’s history dates back almost a decade to a Seattle meeting of astronomers called “Revisiting the Habitable Zone” convened by , principal investigator of the UW-based , with Barnes. The habitable zone is the swath of space around a star that allows for orbiting rocky planets to be temperate enough to have liquid water at their surface, giving life a chance.

They recognized at the time, Barnes said, that knowing if a planet is within its star’s habitable zone simply isn’t enough information: “So from this meeting we identified a whole host of physical processes that can impact a planet’s ability to support and retain water.”

Barnes discussed VPLanet and presented a tutorial on its use at the recent AbSciCon19 worldwide astrobiology conference, held in Seattle.

The research was done through the Virtual Planetary Laboratory and the source code is available .

Barnes’s other faculty co-authors are astronomy professor ; , professor of atmospheric sciences; and research scientist . Other 91̽��co-authors are doctoral students , , and ; and undergraduate researchers Caitlyn Wilhelm, Benjamin Guyer and Diego McDonald.

Other co-authors are of the Carnegie Institution for Science; of the Flatiron Institute, of the Max Planck Institute for Astronomy in Heidelberg, Germany, of the University of Bern, of the NASA Goddard Space Flight Center and of Weber State University.

The research was funded by a grant from the NASA Astrobiology Program’s Virtual Planetary Laboratory team, as part of the research coordination network, or NExSS.

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For more information, contact Barnes at 206-543-8979 or rkb9@uw.edu.

Grant numbers

VPL under cooperative agreement #NNA13AA93A

NASA grants #NNX15AN35G, #13-13-NA17 0024, and #80NSSC18K0829

NASA Earth and Space Science Fellowship Program grant #80NSSC17K0482

Back then, climate science was not as politically charged as it is today.

Over 17 years, and since the 2008 launch of the UW’s College of the Environment, the program has evolved into a campuswide, interdisciplinary, student-driven program on climate change research, communication and action. A recent in Eos, published by the American Geophysical Union, looks back at the program’s unique history.

“A lot of schools have created a climate master’s degree. We’re really trying to give students who are getting disciplinary degrees the added benefit of the climate community and content,” said , who has administered the program since its launch. “It’s a very different program, so trying to explain it to people deserves more than two sentences.”

The program incorporates both traditional academic elements and more outwardly-focused, community-focused aspects.

Central to the program is a that allows 91̽��students to add an interdisciplinary twist to their graduate education. Each student must take an introductory climate science course, that’s now available in three options for students with different levels of mathematical background.

The departments of atmospheric sciences, oceanography, Earth and space sciences, marine affairs and civil and environmental engineering are, of course, well represented. But the certificate program also attracts students in the Department of Philosophy, the Evans School of Public Policy, and even the Foster School of Business.

“This model works because climate is such an integrator across disciplines. And it’s becoming more and more so,” said former director , a professor of oceanography. “The PCC helps people get outside the disciplinary bubble, and that’s where a lot of the innovation is happening.”

Since the program began, each certificate student has done a climate-related outreach project. That effort is assessed and sometimes repeated to better reach a broader audience.

The projects run the gamut. A public policy graduate student studied the possibility of to the Puget Sound region, and presented her paper to city and county officials who plan utilities infrastructure. In 2016, a graduate student in marine affairs created outreach videos filmed in Alaska’s Prince William Sound. Other projects include meditation workshops focused on climate change, art projects, and presentations to union leaders on how climate change will affect working conditions in the future.

Many Program on Climate Change events bring people together. An annual , now in its third year, will take place April 27. Graduate students and postdoctoral researchers will give short, research-based talks to an audience that typically includes undergraduates, faculty members and friends.

The program also hosts more regular that are open to its members and the wider community. A recent gathering was a screening of a made by a retired oceanographer from the Applied Physics Laboratory. On Tuesday, April 16, the group will host a forum on to the public using social media.

Some graduate students have chosen outreach projects that contribute to the effort, creating curriculum for local high schools. A former graduate student made a recipe for creating an ice core that students could probe for chemical clues. Two current graduate students designed and taught a high school curriculum on geoengineering.

A current initiative by a 91̽��faculty member and his graduate students is expanding a simple computer model developed to teach climate modeling in high schools. They will meet May 18 with middle- and high-school teachers to work on bringing the model to classes.

“It’s important that these workshops are two-way,” Bertram said. “The researchers are presenting their content, but they’re also learning from the teachers, who might say: ‘That’s not going to work in my classroom.'”

In 2011 the program launched an in climate that includes a seminar series focusing on a different climate-related topic each year – this winter looked at sea-level rise. While the seminar topic is intended to be of interest to the broader 91̽��community and program members, those enrolled in the minor do writing assignments, including blog posts, a literature review and a one-page policy document.

Graduate students in the program organize an annual climate conference sponsored by the program and other 91̽��departments and units, with increasing levels of funding from the National Science Foundation. That conference now alternates between the 91̽��and the Massachusetts Institute of Technology, and is open to graduate students at both institutions. Last fall’s event, held at UW’s Center for Sustainable Forestry at Pack Forest, was the biggest yet.

“The students are more self-organizing than ever before,” said program director , a professor of atmospheric sciences. “I think their vision of what they can do in the world is much bigger.”

Even as the program takes stock and looks back at its history, organizers are continually experimenting. A recently developed “climate postdocs group” hosts weekly coffee meetings for 91̽��postdoctoral students working on climate change.

“There are not many institutions that have a large enough community of climate-related faculty and students to convene something like this,” Thompson said. “The most important element, I think, is creating this intangible community around climate.”

Other co-authors of the recent Eos paper are founding director , a professor emeritus of oceanography, and former director , a professor of atmospheric sciences.

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For more information, contact Bertram at mab23@uw.edu or 206-543-6521 and Bitz at bitz@uw.edu.

is a 91̽��professor in the atmospheric sciences department and director of the Program on Climate Change. She was recognized for her work studying the Arctic. Bitz’s research looks at the role of sea ice in the climate system and high-latitude climate and climate change. She also studies the predictability of Arctic sea ice and she co-leads the .

Bitz earned her doctorate in atmospheric sciences at the 91̽��in 1997 and has worked at the 91̽��since 1999.

She’ll be among the new fellows recognized during a December meeting in Washington, D.C.

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Aspects of an otherwise Earthlike planet’s tilt and orbital dynamics can severely affect its potential habitability — even triggering abrupt “snowball states” where oceans freeze and surface life is impossible, according to new research from astronomers at the 91̽��.

The research indicates that locating a planet in its host star’s “habitable zone” — that swath of space just right to allow liquid water on an orbiting rocky planet’s surface — isn’t always enough evidence to judge potential habitability.��

, lead author of a paper to be published in the Astronomical Journal, said he and co-authors set out to learn, through computer modeling, how two features — a planet’s obliquity or its orbital eccentricity — might affect its potential for life. They limited their study to planets orbiting in the habitable zones of “G dwarf” stars, or those like the sun.

A planet’s is its tilt relative to the orbital axis, which controls a planet’s seasons; is the shape, and how circular or elliptical — oval — the orbit is. With elliptical orbits, the distance to the host star changes as the planet comes closer to, then travels away from, its host star.

Deitrick, who did the work while with the UW, is at the University of Bern. His 91̽��co-authors are atmospheric sciences professor , astronomy professors , and and graduate student , with help from undergraduate researcher Caitlyn Wilhelm.

The Earth hosts life successfully enough as it circles the sun at an axial tilt of about 23.5 degrees, wiggling only a very little over the millennia. But, Deitrick and co-authors asked in their modeling, what if those wiggles were greater on an Earthlike planet orbiting a similar star?

Previous research indicated that a more severe axial tilt, or a tilting orbit, for a planet in a sunlike star’s habitable zone — given the same distance from its star — would make a world warmer. So Deitrick and team were surprised to find, through their modeling, that the opposite reaction appears true.

“We found that planets in the habitable zone could abruptly enter ‘snowball’ states if the eccentricity or the semi-major axis variations — changes in the distance between a planet and star over an orbit — were large or if the planet’s obliquity increased beyond 35 degrees,” Deitrick said.

The new study helps sort out conflicting ideas proposed in the past. It used a sophisticated treatment of ice sheet growth and retreat in the planetary modeling, which is a significant improvement over several previous studies, co-author Barnes said.

“While past investigations found that high obliquity and obliquity variations tended to warm planets, using this new approach, the team finds that large obliquity variations are more likely to freeze the planetary surface,” he said. “Only a fraction of the time can the obliquity cycles increase habitable planet temperatures.”

Barnes said Deitrick “has essentially shown that ice ages on exoplanets can be much more severe than on Earth, that orbital dynamics can be a major driver of habitability and that the habitable zone is insufficient to characterize a planet’s habitability.” The research also indicates, he added, “that the Earth may be a relatively calm planet, climate-wise.”

This kind of modeling can help astronomers decide which planets are worthy of precious telescope time, Deitrick said: “If we have a planet that looks like it might be Earth-like, for example, but modeling shows that its orbit and obliquity oscillate like crazy, another planet might be better for follow-up” with telescopes of the future.”

The main takeaway of the research, he added, is that “We shouldn’t neglect orbital dynamics in habitability studies.”

Other co-authors are , a former 91̽��post-doctoral researcher now with the LESIA Observatoire de Paris; and John Armstrong of Weber State University, who earned his doctorate at the UW.

The research used storage and networking infrastructure provided by the Hyak supercomputer system at the UW, funded by the UW’s Student Technology Fee. The work was funded by the NASA Astrobiology Institute through the UW-based .

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For more information, contact Deitrick at deitrr@astro.washington.edu or russell.deitrick@csh.unibe.ch; or Barnes at rory@astro.washington.edu.

Agreement number: NNA13AA93A

A dramatic drop in Antarctic sea ice almost a year ago, during the Southern Hemisphere spring, brought its maximum area down to its lowest level in 40 years of record keeping. Ocean temperatures were also unusually warm. This exceptional, sudden nosedive in Antarctica differs from the long-term decline in the Northern Hemisphere. A new 91̽�� study shows that the lack of Antarctic sea ice in 2016 was in part due to a unique one-two punch from atmospheric conditions both in the tropical Pacific Ocean and around the South Pole.

The was published Aug. 24 in Geophysical Research Letters.

“This combination of factors, all these things coming together in a single year, was basically the ‘perfect storm,’ for Antarctic sea ice,” said corresponding author , a 91̽��postdoctoral researcher in atmospheric sciences. “While we expect a slow decline in the future from global warming, we don’t expect such a rapid decline in a single year to happen very often.”

The area of sea ice around Antarctica at its peak in late 2016 was 2 million square kilometers (about 800,000 square miles) less than the average from the satellite record. Statistically, this is three standard deviations away from the average — an event that would be expected to occur randomly just once every 300 years.

The record low was not predicted by climate scientists, so 91̽��researchers looked at the bigger picture in ocean and atmospheric data to explain why it happened.

The previous year, 2015-16, had a very strong El Niño in the tropical Pacific Ocean. Nicknamed the “,” the event was similar to other monster El Niños in 1982-83 and 1997-98. Unlike the 1997-98 event, however, it was only followed by a relatively weak La Niña in 2016.

Far away from the tropics, the tropical El Niño pattern creates a series of high- and low-pressure zones that cause unusually warm ocean temperatures in Antarctica’s eastern Ross, Amundsen and Bellingshausen seas. But in 2016, when no strong La Niña materialized, researchers found that these unusually warm surface pools lingered longer than usual and affected freeze-up of seawater the following season.

“I’ve spent many years working on tropical climate and El Niño, and it amazes me to see its far-reaching impacts,” Stuecker said.

Meanwhile, observations show that the winds circling Antarctica were unusually weak in 2016, meaning they did not push sea ice away from the Antarctic coast to make room for the formation of new ice. This affected ice formation around much of the Southern Ocean.

“This was a really rare combination of events, something that we have never seen before in the observations,” Stuecker said.

The researchers analyzed 13,000 years of climate model simulations to study how these unique conditions would affect the sea ice. Taken together, the El Niño pattern and Southern Ocean winds explain about two-thirds of the 2016 decline. The rest may be due to , which a previous paper suggested had broken up ice floes.

Scientists predict Antarctica’s ocean will be one of the to experience global warming. Eventually the Southern Ocean’s surface will begin to warm, however, and then sea ice there will begin its more long-term decline.

“Our best estimate of the Antarctic sea ice turnaround point is sometime in the next decade, but with high uncertainty because the climate signal is small compared to the large variations that can occur from one year to the next,” said co-author , a 91̽��professor of atmospheric sciences.

Stuecker noted that this type of big, rare weather event is useful to help understand the physics behind sea ice formation, and to learn how best to explain the observations.

“For understanding the climate system we must combine the atmosphere, ocean and ice, but we must focus on more than a specific region,” Stuecker said. “If we want to understand sea ice in Antarctica, we cannot just zoom in locally — we really have to take a global perspective.”

The other co-author is , a 91̽��assistant professor of atmospheric sciences and oceanography. The research was funded by the National Science Foundation and a National Oceanographic and Atmospheric Administration’s Climate and Global Change Postdoctoral Fellowship Program, administered by the University Corporation for Atmospheric Research’s for the Advancement of Earth System Science.

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For more information, contact Stuecker at stuecker@atmos.washington.edu or Bitz at bitz@uw.edu and reach either scientist at 206-543-1339.

The study, led by Colorado’s National Center for Atmospheric Research with co-authors at the 91̽�� and other institutions, may resolve a longstanding mystery: Why is Antarctic sea ice expanding despite climate-related global warming?

The study offers evidence that the current negative phase of the , which brings cooler-than-average sea surface temperatures in the tropical eastern Pacific, has created favorable conditions for additional Antarctic sea ice growth since 2000.

The winter sea ice around Antarctica is particularly susceptible to its influence.

“Compared to the Arctic, global warming causes only weak Antarctic sea ice loss, which is why the IPO can have such a striking effect in the Antarctic,” said co-author , a 91̽��professor of atmospheric sciences who studies sea ice. “There is no comparable natural variability in the Arctic that competes with global warming.”

The sea ice surrounding Antarctica has been slowly increasing in area since the satellite record began in 1979. But the rate of increase rose by nearly fivefold between 2000 and 2014, following the IPO’s 1999 transition to a negative phase.

The new study used climate models that capture this transition to show that when the IPO changes phase, from positive to negative or vice versa, it touches off a chain reaction of climate impacts that may ultimately affect sea ice formation at the bottom of the world.

When the IPO transitions to a negative phase, the sea surface temperatures in the tropical eastern Pacific become somewhat cooler than average when measured over a decade or two. These sea surface temperatures, in turn, change tropical precipitation, which drives large-scale changes to the winds that extend all the way down to Antarctica.

The ultimate impact is a deepening of a low-pressure system off the coast of Antarctica known as the Amundsen Sea Low. Winds generated on the western flank of this system blow sea ice northward, away from Antarctica, helping to enlarge the extent of sea ice coverage.

“The climate we experience during any given decade is some combination of naturally occurring variability and the planet’s response to increasing greenhouse gases,” said lead author , a scientist at the National Center for Atmospheric Research. “It’s never all one or the other, but the combination, that is important to understand.”

The authors suspect that in 2014 the IPO began to change from a negative to positive phase, and that sea ice growth may begin to slow and winter sea ice may shrink over the next decade as the oscillation switches to its positive phase and global warming continues.

Other co-authors are Julie Arblaster of NCAR and Monash University in Australia, Christine Chung at the Australian Bureau of Meteorology and Haiyan Teng at NCAR. The study was funded by the U.S. Department of Energy and the National Science Foundation.

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Adapted from an NCAR press release; read the .

91̽�� polar scientists are on Alaska’s North Slope this week for the 2016 Barrow Sea Ice Camp. Supported by the National Science Foundation, the event brings together U.S.-based sea ice observers, satellite experts and modelers at various career stages to collect data and discuss issues related to measuring and modeling sea ice. The goal is to integrate the research community in order to better observe and understand the changes in Arctic sea ice.

Check out the group’s , written by a who’s taking his first trip into the field, or follow updates on . The group is based just north of Barrow from May 26 to June 2, in the northernmost point in the U.S.

91̽��participants include , a 91̽��professor of atmospheric sciences, , an oceanographer at the 91̽��Applied Physics Laboratory, , a physicist at the Applied Physics Laboratory, , a 91̽��graduate who is now a research assistant at APL, 91̽��atmospheric sciences postdoctoral researchers and , and , an anthropology student who has a visiting appointment at APL.