A Super El Niño is coming. Here’s how a hotter ocean could change the weather near you

Andrew Freedman, 

CNN
Tue, April 7, 2026 



People gather to watch the sunset at La Jolla's Windansea Beach during a winter heat wave on January 31, in San Diego, California. A Super El Niño could result in record-breaking heat next winter, as well. - Kevin Carter/Getty Images


Get ready to hear a lot more about El Niño during the next several months — and maybe even longer — as the infamous climate cycle returns again, developing and intensifying in the Pacific Ocean near the equator. If it forms as expected, this El Niño will redraw global weather maps, sparking flooding for some and drought and wildfires for others — all while simultaneously speeding up the pace of global warming.

There are increasing indications that an El Niño is not only imminent — setting in by late summer or early fall — but that it could be a significant one, too.

In fact, this might even qualify as a “Super El Niño,” which would significantly increase impacts felt around the world. Such extremely intense El Niños are rare.



To declare an El Niño, in general, ocean temperatures in a particular region of the tropical Pacific must clear 0.5 degrees Celsius above the long-term average. A Super El Niño, in contrast, happens when temperatures are more than 2 degrees C above the average. Some typically reliable computer models, like the European modeling suite, are projecting just such an outcome for this go-around.
The baddest kids in town

El Niño and La Niña, names that translate to “the Boy” and “the Girl”, are recurring climate cycles in the tropical Pacific Ocean that happen every few years and can have profound effects on global weather patterns. In the case of El Niño, the cycle can bring both flooding and drought to different parts of Africa, help pummel the U.S. West Coast with winter storms and lead to more heat extremes globally.

El Niño is characterized by unusually warm waters along the equatorial tropical Pacific Ocean, and a related series of shifts in winds and precipitation patterns in the atmosphere. It is a so-called coupled phenomenon, meaning that to get an El Niño, both the ocean and the atmosphere must be responding to one another in characteristic ways.

A map of ocean temperature differences from normal during a strong El Niño. Red colors mean the ocean water is warmer than normal; blue means it's cooler. - NOAA

The atmosphere tends to react to the warmer waters by shifting areas of heavy precipitation closer to that hot region of the ocean. The trade winds that typically blow from east to west near the equator can slacken and then reverse direction as well. Those shifts are significant enough to affect weather around the world, like a series of dominoes toppling over.

Right now, huge volumes of unusually warm water are spreading under the ocean surface from the Western to the Eastern tropical Pacific, where that water slowly rises to the surface in a clear precursor to El Niño. Periodic areas of wind blowing from the west to the east have helped transport this water, in what are appropriately known as westerly wind bursts.

While El Niño and La Niña, El Niño’s cooler sibling, are fascinating from a meteorological perspective, we care about them because of the ways in which they can affect extreme weather events around the world. In fact, they can cause billions of dollars in damages, and a stronger El Niño would likely make the usual impacts more severe.

Spotting an El Niño in formation and predicting its evolution “gives us an early heads up on changing risks for many weather-related phenomena, including floods, droughts, heatwaves, hurricanes and severe thunderstorms,” said Nat Johnson, a meteorologist at the National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory. “These weather and climate impacts modify crop yields, disease spread, coral bleaching, fisheries and many other parts of the earth system that affect our daily lives.”

There’s still a lot of uncertainty around the upcoming El Niño, including a range of forecast outcomes, especially when it comes to intensity, Johnson said. To cloud matters a bit further; computer model projections made during the spring tend to have lower accuracy than projections made at other times of the year, a phenomenon known as the spring prediction barrier.

People flock Baker Beach near the Golden Gate Bridge as heat advisory issued in San Francisco, California, on March 16. - Tayfun Coskun/Anadolu/Getty Images
Hot and hotter

In the U.S., El Niño tends to have its peak effects during the winter months, when it can send a fusillade of storms into parts of California and along the southern tier of the U.S., bringing the risk of flooding.

It can also speed up winds in the upper atmosphere across the tropical Atlantic Ocean during the fall. This causes wind shear to increase, and this can tear apart nascent tropical storms and hurricanes — putting a damper on the Atlantic hurricane season.

In addition, strong El Niño’s have also been linked to heat waves in the U.S. and other parts of the world.

Globally, El Niño is known to tilt the odds in favor of drought and heat waves in Australia, where it can also raise wildfire risks. Other areas prone to drought during El Niño include northern sections of South America (including parts of the Amazon rainforest), central and southern Africa and India. El Niño can also cause too much rain to fall, with favored areas for flooding outside of the U.S. including southeastern South America, the Horn of Africa, Iran, Afghanistan and other parts of south-central Asia.

When it comes to the climate, El Niño tends to release enormous amounts of heat stored in the oceans back into the atmosphere, boosting global average surface temperatures. If a strong El Niño does form and continues through the winter, then it is almost assured that either 2026, 2027 or both years will set new records for the warmest year since instrument data began in the 19th century.

The globe is already warming at an accelerating rate, and an intense El Niño would speed that up even faster, at least for a few years. If climate change is like ascending an escalator, with some years warmer than others, an El Niño year is equivalent to jumping up and down while riding on that escalator — reaching record new heights, albeit briefly.

The last El Niño, which was not a Super El Niño, resulted in 2024 being the current holder of the warmest-year title. The last Super El Niño occurred in 2015-2016, with others in 1997-98, and 1982-83. Super El Niños are not a technical designation from NOAA but instead are an informal definition used by some forecasters and the media to refer to a very strong El Niño

Meteorologists will be closely watching as the Pacific waters heat up to see just how strong an El Niño we get. If the European model is proven correct, it could even be the strongest El Niño on record.

 

Much of humanity may face hot-dry extremes five times more often by end-century

The increase may hit nearly 30% of the global population with extreme events more dangerous than heat or drought alone, especially in low-income tropical nations

American Geophysical Union

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WASHINGTON — In their current state, climate policies around the world could leave a significant chunk of the global population exposed to simultaneous extreme heat and drought over five times more often by the end of this century than during the mid-to-late 20th century.  

In a new study, researchers project the increase will affect 28% of the global population overall, concentrated in low-income, tropical nations that have contributed only a small fraction of humanity’s greenhouse gas emissions to date. 

“Heat and drought amplify each other,” said Di Cai, a climate scientist at the Ocean University of China and lead author of the study. “In compound hot-dry extremes, they lead to water restrictions and unstable food prices. For outdoor workers, it is dangerous.” 

The study will appear Tuesday, April 7 in Geophysical Research Letters, AGU’s journal for high-impact, innovative, and timely articles on major advances across the geosciences. 

Amplified Extremes 

When heat and drought strike together, the damage often exceeds the sum of what they can inflict separately. Wildfire risk, agricultural losses, and heat-related mortality can all spike. 

These extreme combos are already on the rise. When the researchers divided Earth’s land into cells on a grid and compared heat and drought occurrence in each cell, they found that, on geographical average, Earth’s land areas weathered roughly four hot-dry events per year from 2001 to 2020. By their estimates, that’s about twice as often as in the preindustrial period from 1850 to 1900. 

To see how conditions might evolve through the end of this century, the team analyzed 152 existing simulations based on eight climate models, considering various scenarios of population growth and global warming outlined in the Sixth Assessment Report by the Intergovernmental Panel on Climate Change. For this study, they defined hot-dry events as days with a high temperature in the top 10% and at least moderate drought, both relative to records from the 1961 to 1990 baseline. 

The effort required processing terabytes of data, a significant challenge. “The more chaotic the climate becomes, the more difficult it becomes to make forecasts,” said Monica Ionita, a climatologist at the Alfred Wegener Institute and senior author of the study. “It’s very difficult to keep up with what’s going on now.” 

In the climate and population growth scenario most aligned with our current trajectory, the team found, hot-dry extremes become “heightened” (over five times more probable on any given day than during 1961 to 1990) for 28% of the global population — nearly 2.6 billion people — by the 2090s. For comparison, they expect only about 6.6% to suffer that level of exposure in the 2030s. 

“When you get to almost 30% of the global population affected by this, it’s very critical. It should make us consider much, much more deeply our actions in the future,” Ionita said. She had anticipated a slightly slower pace of change, ending at a figure of maybe 10% or 15%. “By the end or middle of the century, maybe my children will not be able to experience the life that I have now.” 

Some reap what others sow 

Globally, compound hot-dry extremes may strike nearly 10 times per year on average by end-century, with the longest lasting around 15 days — increases of 2.4 and 2.7 times from the conditions of the past 25 years, respectively. Human emissions of greenhouse gases drive those changes: When the researchers analyzed simulations with only natural forces at play, no significant trends in the frequency or duration of hot-dry extremes emerged. 

However, those who emit the most likely won’t suffer the greatest impacts. According to the geographical distribution of risk in the simulations, low-income nations around the equator and tropics, including islands such as Mauritius and Vanuatu, will feel the most exacerbated hot-dry extremes despite contributing far fewer emissions than wealthier nations. For context, the team estimated the climate impact from the carbon 1.2 average U.S. citizens emit over their lifetimes could expose one additional person to heightened hot-dry extremes by the end of the century. 

“For lower-income countries, there is a huge unfairness here,” Cai said. “It’s hard to fund air conditioning. It’s hard to fund health care. There is no backup if water runs out. It’s not just a climate science issue; it is about basic, daily life.” 

Limiting emissions could avert a lot of risk, the researchers found. If all nations fully implement the climate action plans they contributed under the Paris Agreement, as well as more binding long-term pledges, about 18% of the global population would face heightened exposure to hot-dry extremes by the century’s end. That equates to roughly 1.7 billion people, nearly a third fewer than the number under the current trajectory. 

“The choices we make today will directly affect the daily lives of billions of people in the future,” Cai said. 

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Notes for journalists:    

This study is published in Geophysical Research Letters, an open access AGU journal. This study is under embargo until Tuesday, April 7, 2026 at 13:00 UTC. Journalists may request an embargoed copy of the study by emailing news@agu.org. The study will be available to view and download at this link after the embargo lifts: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025GL118822

Paper title:

“Compound Hot-Dry Extremes Amplify Disproportionate Climate Risks for Low-Income Nations”  

Authors:    

• Di Cai, Frontier Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao, China; Physical Oceanography Laboratory, Ocean University of China, Qingdao, China; Alfred Wegener Institute Helmholtz Center for Polar and Marine Research, Bremerhaven, Germany 

• Gerrit Lohmann, Alfred Wegener Institute Helmholtz Center for Polar and Marine Research, Bremerhaven, Germany; University of Bremen, Bremen, Germany 

• Xianyao Chen, Frontier Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao, China; Physical Oceanography Laboratory, Ocean University of China, Qingdao, China; Key Laboratory of Transparent Arctic, Ocean University of China, Qingdao, China; Laoshan Laboratory, Qingdao, China

• Monica Ionita, Alfred Wegener Institute Helmholtz Center for Polar and Marine Research, Bremerhaven, Germany; Stefan cel Mare University of Suceava, Suceava, Romania 

---

Journal

Geophysical Research Letters

DOI

10.1029/2025GL118822 

Article Title

Compound Hot-Dry Extremes Amplify Disproportionate Climate Risks for Low-Income Nations

Article Publication Date

7-Apr-2026

 

Wildfires An Increasing Threat For Species During Climate Change

 April 7, 2026  

By Eurasia Review

Wildfires are becoming more frequent and are ravaging new parts of the world due to global warming. A study led by researchers from the University of Gothenburg shows that this change is increasing the vulnerability of thousands of plants, animals and fungi.

As global temperatures rise, the incidence of wildfires is increasing in many regions. This is mainly because higher average temperatures and changing weather conditions are drying out land and vegetation, making them more flammable. The study in Nature Climate Change shows that wildfires can break out closer to the poles than before. In some areas, the fire seasons may also double in length. This is under a medium scenario where the emissions don’t sharply increase or get cut till the end of this century.

“Our research shows that wildfires pose an ever-increasing threat to biodiversity. We find that nearly 84 per cent of species vulnerable to wildfires will face a higher risk by the end of this century,” says Xiaoye Yang, a researcher at the University of Gothenburg and the study’s lead author.

Combines 13 climate models

Previous research into how biodiversity is affected by global climate change has mainly focused on gradual changes to habitats. Less attention has been paid to how climate-driven wildfires affect the long-term survival of plants and animals. 

The research team, including Chalmers University of Technology, combined 13 climate models with a machine learning-based method to forecast changes in the wildfire burned area and the length of the fire season up to the end of this century. They then assessed how these changes affect the risk to species worldwide, based on a Red List from the IUCN (International Union for Conservation of Nature). The Red List includes 9,592 species whose survival is currently threatened by the increasing occurrence and severity of wildfires.

– Species with small ranges are particularly vulnerable. The most affected species are concentrated in South America, South Asia and Australia, and a large proportion of them are already endangered. An increase in the frequency of wildfires could push some of them closer to extinction, says Xiaoye Yang.

Even species that have previously been spared from wildfires are facing a new threat, but there is a lack of research to assess how serious that threat is.

Global trends of increasing risk

The researchers calculated the increase in wildfires based on the IPCC’s various global warming scenarios. Under a moderate scenario involving a temperature rise of around 2.7 degrees compared with pre-industrial levels, the study shows that:

•    The global area affected by wildfires could increase by around 9.3 per cent

•    Fire seasons could be extended by 22.8 per cent

•    Almost 84 per cent of species vulnerable to fire will face an increased risk of wildfires

The study highlights significant regional differences. Whilst the risk of wildfires is increasing in many parts of the world, certain regions in Africa may see a reduction in the area affected by fires due to a wetter climate in the future.

Climate action can reduce risk

The researchers also show that measures to limit emissions can significantly reduce the occurrence of wildfires. Compared with a high-emissions scenario, a future with moderate emissions could reduce the increase in species’ vulnerability to wildfires by more than 60 per cent. Regions such as New Zealand, South America and areas near the Arctic would benefit most from reduced emissions.

“Current conservation strategies for vulnerable plants and animals risk underestimating future threats if they do not take into account disturbances such as wildfires,” says Xiaoye Yang.

Wildfires an increasing threat for species during climate change

University of Gothenburg

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image: 

The ongoing climate change will lead to more wildfires. And this is increasing the vulnerability of thousands of plants, animals and fungi.

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Credit: Photo: Tongxin Hu

Wildfires are becoming more frequent and are ravaging new parts of the world due to global warming. A study led by researchers from the University of Gothenburg shows that this change is increasing the vulnerability of thousands of plants, animals and fungi.

As global temperatures rise, the incidence of wildfires is increasing in many regions. This is mainly because higher average temperatures and changing weather conditions are drying out land and vegetation, making them more flammable. The study in Nature Climate Change shows that wildfires can break out closer to the poles than before. In some areas, the fire seasons may also double in length. This is under a medium scenario where the emissions don’t sharply increase or get cut till the end of this century.

“Our research shows that wildfires pose an ever-increasing threat to biodiversity. We find that nearly 84 per cent of species vulnerable to wildfires will face a higher risk by the end of this century,” says Xiaoye Yang, a researcher at the University of Gothenburg and the study’s lead author.

Combines 13 climate models

Previous research into how biodiversity is affected by global climate change has mainly focused on gradual changes to habitats. Less attention has been paid to how climate-driven wildfires affect the long-term survival of plants and animals. 

The research team, including Chalmers University of Technology, combined 13 climate models with a machine learning-based method to forecast changes in the wildfire burned area and the length of the fire season up to the end of this century. They then assessed how these changes affect the risk to species worldwide, based on a Red List from the IUCN (International Union for Conservation of Nature). The Red List includes 9,592 species whose survival is currently threatened by the increasing occurrence and severity of wildfires.

– Species with small ranges are particularly vulnerable. The most affected species are concentrated in South America, South Asia and Australia, and a large proportion of them are already endangered. An increase in the frequency of wildfires could push some of them closer to extinction, says Xiaoye Yang.

Even species that have previously been spared from wildfires are facing a new threat, but there is a lack of research to assess how serious that threat is.

Global trends of increasing risk

The researchers calculated the increase in wildfires based on the IPCC’s various global warming scenarios. Under a moderate scenario involving a temperature rise of around 2.7 degrees compared with pre-industrial levels, the study shows that:

•    The global area affected by wildfires could increase by around 9.3 per cent

•    Fire seasons could be extended by 22.8 per cent

•    Almost 84 per cent of species vulnerable to fire will face an increased risk of wildfires

The study highlights significant regional differences. Whilst the risk of wildfires is increasing in many parts of the world, certain regions in Africa may see a reduction in the area affected by fires due to a wetter climate in the future.

Climate action can reduce risk

The researchers also show that measures to limit emissions can significantly reduce the occurrence of wildfires. Compared with a high-emissions scenario, a future with moderate emissions could reduce the increase in species’ vulnerability to wildfires by more than 60 per cent. Regions such as New Zealand, South America and areas near the Arctic would benefit most from reduced emissions.

“Current conservation strategies for vulnerable plants and animals risk underestimating future threats if they do not take into account disturbances such as wildfires,” says Xiaoye Yang.

 

Figure: Projected changes in wildfire burned area. Percentage increase in annual burned area relative to the reference period (1999–2014), projected for 2081–2100 under SSP2-4.5.

Credit

Xiaoye Yang

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Journal

Nature Climate Change

DOI

10.1038/s41558-026-02600-5 

Method of Research

Computational simulation/modeling

Article Title

Wildfire Risk for Species under Climate Change

Article Publication Date

6-Apr-2026

 

Wildfires accelerate winter snowmelt in Oregon's western Cascades, PSU study finds

Portland State University

The Pacific Northwest has seen below-normal snow this season — and new research from Portland State University suggests that the region's snowmelt-dependent water resources could face growing challenges in the years ahead as forest fires and winter rainstorms become more frequent.

Researchers in PSU's Snow Hydrology Lab, led by Kelly Gleason, an associate professor of eco-hydro-climatology in the School of Earth, Environment & Society, found that snow in burned areas of Oregon's western Cascades melted much faster during midwinter rain-on-snow events than snow in nearby unburned areas. 

Rain-on-snow events — when warm rain falls on an existing snowpack — can trigger rapid melting and increase flood risk downstream in just a matter of days. In the Pacific Northwest, that matters because mountain snow acts as critical seasonal water storage, refilling reservoirs, refreshing municipal and irrigation water supplies, producing hydroelectric power and providing habitat during the drier summer months. The new study shows that wildfire damage can intensify those impacts, reducing how long snow can hold onto water.

Wildfires open forest canopies, allowing more sunlight to reach the snow, while burned debris on the snow surface makes the snow absorb more and reflect less of that light. Together, those changes reduce the snowpack’s “cold content” — the built-in buffer that allows snow to warm up without immediately melting.

Sage Ebel, the study's lead author and a doctoral student in PSU's Earth, Environment & Society program, compares that cold content to a sponge.

"If a sponge has a lot of space, it can absorb water before anything drains out," Ebel said. "But if it's already saturated, water runs out right away. A snowpack with a lot of cold content can absorb heat before it starts melting. What we're finding is that small changes in short- and long-wave radiation in the burned sites are keeping that cold content lower than in unburned areas, making them vulnerable to snowmelt during rain-on-snow events."

Ebel and Gleason installed snow monitoring stations across high, mid and low elevations in the Breitenbush River watershed, 80% of which burned during the 2020 Lionshead fire. In 2023 and 2024, burned sites lost roughly twice as much snow during these rain-on-snow events as nearby unburned areas. Snowpacks at mid-elevations were most vulnerable, with rain-on-snow-driven melt accounting for 26% more of the total annual melt in burned forests.

"The impacts of climate change are exacerbated in the burned forest," Ebel said. "There's less capacity to absorb small changes in warming or inputs from rain than in unburned areas. As the area of burned forests increases with climate change, those effects could have widespread consequences for the water reserves we rely on across the West."

Faster winter melt from burned areas adds new stress to those systems, forcing water managers to balance flood preparedness with long-term water storage in a warming climate.

The researchers say understanding how wildfires and rain-on-snow events interact is essential for refining snowmelt models, improving flood forecasting and planning for more reliable water supplies in the future.

The study was published in the journal Environmental Research Communications. The findings are one example of the kind of applied, place-based research underway in PSU's School of Earth, Environment & Society, which launched this fall uniting multiple departments to encourage collaboration on complex, interconnected issues such as climate change.

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Journal

Environmental Research Communications

DOI

10.1088/2515-7620/ae550d 

Method of Research

Data/statistical analysis

Subject of Research

Not applicable

Article Title

Inclusive Publishing Trusted Science, find out more. ER-Logo.png, find out more. PLP-Logo-2.png, find out more. Letter • The following article isOpen access Forest fires increase vulnerability to midwinter rain-on-snow snowmelt in the western Oregon Cascades

Article Publication Date

31-Mar-2026

 

Low snowpack kindles more severe wildfires, western study finds

“It’s only March, and a wet spring could still make a lot of difference”

Western Colorado University

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Across much of the Rocky Mountain West, a winter of record-breaking high temperatures and historically low snowfall has forced people to think about having less water this spring. But it could also mean more severe wildfires this summer, according to new research from Western Colorado University.

In a paper published in the journal Environmental Research Letters, researchers from Western’s Clark School of Environment and Sustainability found that declining snowpack not only extends the fire season but also increases the severity of forest fires.

Analyzing 36 years of snowpack and wildfire data across forests in the western United States, the researchers identified two related but distinct patterns. Early snowmelt was strongly associated with earlier fire seasons and greater total area burned. But low snow water content – the amount of water stored in winter snowpack – was linked to more severe fires, leading to higher tree mortality, greater impacts to ecosystem functions, and increased likelihood of long-term forest loss.

“Snowpack acts as a kind of seasonal water savings account for forests,” the study’s lead author, Dr. Jared Balik, a Western research scientist, said. “When that account runs low, soils dry out earlier, vegetation loses moisture, and forests become more vulnerable to severe fire.”

While previous research has connected warming temperatures and earlier snowmelt to longer fire seasons, this new research shows that reduced snow storage also influences how destructively forests burn.

Years with low snowpack were consistently associated with higher burn severity across watersheds studied from 1985 to 2021. This year, nearly every river basin in the West is experiencing low snowpack.

The findings carry particular weight for southwestern watersheds, including the Rio Grande and Colorado River basin, where long-term snowpack declines have been most pronounced.

The research also highlights the role of global climate patterns like El Niño and La Niña. Depending on the region, such phenomena can increase or decrease winter snowpack and influence the severity of the fire seasons that follow.

However, the long-term trend points toward warming winters and reduced snowpack, leading to earlier melt and more high-severity forest fires.

High-severity fires can trigger cascading ecological effects, according to the paper, such as post-fire flooding and debris flows, and may increase the likelihood that forests convert to shrubland or grassland under warmer, drier conditions.

The researchers, including Balik, Western professor Dr. Jonathan Coop, and Dr. Sean Parks of Ariel Re, say snowpack conditions could serve as an early indicator of fire severity risk, helping land managers adjust thinning, prescribed fire, and preparedness strategies based on winter conditions.

“As snowpack continues its long-term decline, we should expect not just more fire, but more severe fire,” Coop said. “Understanding those connections not only allows us to plan ahead in years like this one but also compels forest management interventions like prescribed fire that can reduce wildfire impacts.”

Despite a gloomy outlook for the upcoming wildfire season, there is still reason to be hopeful. “It’s only March, and a wet spring could still make a lot of difference,” Balik said.

To read the full study, visit https://iopscience.iop.org/article/10.1088/1748-9326/ae4e4a.  For more information about studying the science of wildfires at Western, visit western.edu.

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Journal

Environmental Research Letters

DOI

10.1088/1748-9326/ae4e4a 

Method of Research

Meta-analysis

Subject of Research

Not applicable

Article Title

Snowpack decline kindles more severe fire in the western United States

Article Publication Date

23-Mar-2026

 

New research highlights the importance of sublimation for the Rocky Mountain snowpack

In a year of historic snow drought for the region, a study in Geology shows that climate change can impact the rate that snow disappears into the atmosphere

Geological Society of America

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This past winter, the Rocky Mountains experienced an historic snow drought, a worrying development for the tens of millions of people in the arid American West who depend on snowmelt for water. Now, a new study in the journal Geology investigates the geologic history of a surprising process that might be making the problem even worse: sublimation, the process by which frozen water transforms directly into water vapor, skipping the liquid phase altogether.

“We all see the effects of sublimation when we go to the freezer and pull out the ice cube tray,” says Jeffrey Munroe, a geologist at Middlebury College and the University of Innsbruck and lead author of the study. “We swear we made ice a few weeks ago and yet the tray is empty or the ice cubes are half gone.” 

In the Rocky Mountains, sublimating snow means that less ice melts to water that makes it into the reservoirs and rivers people depend on.

Munroe and his co-author, Christoph Spötl, studied a cave ice deposit in northern Utah, and found evidence that from about 6,000 to 600 years ago, the disappearance of the winter snowpack due to sublimation systematically increased from about 30% to 45%. While this record doesn’t necessarily show how sublimation might impact the snowpack in this or future years, it does demonstrate the magnitude of the process in the long-term and how its impact can vary over time.

The ice in Bear Ice Cave forms when melting of the seasonal snowpack saturates the ground in the spring. Because the floor of the cave stays below freezing year-round, water dripping into the cave from the surface freezes and forms ice. During the rest of the year, the soil is too dry for water to make it to the cave, which means the ice matches the composition of the snow at the end of the winter.

“It sounds improbable,” says Munroe, “but if the geometry of a cave is right, cold air just sinks down into it in the winter and refrigerates it.” In the summer, warm air can’t sink into the depths of the cave, allowing subfreezing temperatures to persist even during warmer months. Nonetheless, cave ice is disappearing fast in a warming climate. Munroe says scientists like himself feel an urgency to study these ice accumulations before they’re gone.

During his first visit to the cave, after descending through an area filled with loose rocks and debris, Munroe noticed his footing was becoming slippery. Eventually, the floor of the cave turned into a steep, icy slope that required ropes to traverse. Then, “all of a sudden you turn around and you’re looking at this impressive cliff of layered ice,” says Munroe. “Geologists love anything that’s layered. You see layers and you’re like, ‘Okay, now we’ve got a story.’”

In this case, that story came from the isotopic composition of the ice, which comes from the melting snow above. Over the duration of the record, the ice became isotopically heavier, meaning the relative proportion of hydrogen and oxygen with an extra neutron increased. Sublimation from the snowpack preferentially removes the lighter isotopes, which turn into water vapor more easily, leaving the remaining snow isotopically heavier. After ruling out other plausible explanations, Munroe and Spötl concluded that an increase in the effectiveness of snow sublimation over time was the most likely driver of the long-term signal they observed in the ice.

Munroe hopes this study highlights the importance of sublimation and helps policy makers better plan for future snow droughts. 

“Sublimation is often just ignored,” he says, “and yet any water manager is going to sit up and take notice if you tell them half the snow that falls in winter might just go back into the air, and that value could change over time.”

Citation: Monroe, J., Spötl, C., 2026, Stable isotopes in cave ice reveal Holocene changes in mountain snowpack sublimation; Geology: https://doi.org/10.1130/G54328.1

About the Geological Society of America

The Geological Society of America (GSA) is a global professional society with more than 18,000 members across over 100 countries. As a leading voice for the geosciences, GSA advances the understanding of Earth's dynamic processes and fosters collaboration among scientists, educators, and policymakers. GSA publishes Geology, the top-ranked “geology” journal, along with a diverse portfolio of scholarly journals, books, and conference proceedings—several of which rank among Amazon’s top 100 best-selling geology titles.

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DOI

10.1130/G54328.1 

Article Title

Stable isotopes in cave ice reveal Holocene changes in mountain snowpack sublimation

Article Publication Date

19-Mar-2026