Forest fires accelerating snowmelt across western U.S., new study finds

Forest fires accelerating snowmelt across western U.S., new study finds

Kelly Gleason, assistant professor of environmental science and management at Portland State University, and crew head out in a recently burned forest to collect snow samples. Credit: Kelly Gleason/Portland State University


 

RENO, Nev. (May 2, 2019) – Forest fires are causing snow to melt earlier in the season, a trend occurring across the western U.S. that may affect water supplies and trigger even more fires, according to a new study by a team of researchers at Portland State University (PSU), the Desert Research Institute (DRI), and the University of Nevada, Reno.

It’s a cycle that will only be exacerbated as the frequency, duration, and severity of forest fires increase with a warmer and drier climate.

The study, published May 2 in the journal Nature Communications, provides new insight into the magnitude and persistence of forest fire disturbance on critical snow-water resources.

Researchers found that more than 11 percent of all forests in the West are currently experiencing earlier snowmelt and snow disappearance as a result of fires.

The team used state-of-the-art laboratory measurements of snow samples, taken in DRI’s Ultra-Trace Ice Core Analytical Laboratory in Reno, Nevada, as well as radiative transfer and geospatial modeling to evaluate the impacts of forest fires on snow for more than a decade following a fire. They found that not only did snow melt an average five days earlier after a fire than before all across the West, but the accelerated timing of the snowmelt continued for as many as 15 years.

“This fire effect on earlier snowmelt is widespread across the West and is persistent for at least a decade following fire,” said Kelly Gleason, the lead author and an assistant professor of environmental science and management in PSU’s College of Liberal Arts and Sciences.

Gleason, who conducted the research as a postdoctoral fellow at the Desert Research Institute, and her team cite two reasons for the earlier snowmelt.

First, the shade provided by the tree canopy gets removed by a fire, allowing more sunlight to hit the snow. Secondly and more importantly, the soot — also known as black carbon — and the charred wood, bark and debris left behind from a fire darkens the snow and lowers its reflectivity. The result is like the difference between wearing a black t-shirt on a sunny day instead of a white one.

In the last 20 years, there’s been a four-fold increase in the amount of energy absorbed by snowpack because of fires across the West.

Research team in snowy forest

Burned forests shed soot and burned debris that darken the snow surface and accelerate snowmelt for years following fire. Image Credit: Nathan Chellman/DRI.

“Snow is typically very reflective, which is why it appears white, but just a small change in the albedo or reflectivity of the snow surface can have a profound impact on the amount of solar energy absorbed by the snowpack,” said co-author Joe McConnell, a research professor of hydrology and head of the Ultra-Trace Ice Core Analytical Laboratory at DRI. “This solar energy is a key factor driving snowmelt.”

For Western states that rely on snowpack and its runoff into local streams and reservoirs for water, early snowmelt can be a major concern.

“The volume of snowpack and the timing of snowmelt are the dominant drivers of how much water there is and when that water is available downstream,” Gleason said. “The timing is important for forests, fish, and how we allocate reservoir operations; in the winter, we tend to control for flooding, whereas in the summer, we try and hold it back.”

Early snowmelt is also likely to fuel larger and more severe fires across the West, Gleason said.

“Snow is already melting earlier because of climate change,” she said. “When it melts earlier, it’s causing larger and longer-lasting fires on the landscape. Those fires then have a feedback into the snow itself, driving an even earlier snowmelt, which then causes more fires. It’s a vicious cycle.”

Gleason will continue to build on this research in her lab at PSU. She’s in the first year of a grant from NASA that’ll look at the forest fire effects on snow albedo, or how much sunlight energy its surface reflects back into the atmosphere.

Funding for the study was provided by the Sulo and Aileen Maki Endowment at the Desert Research Institute. Co-authors also included Monica Arienzo and Nathan Chellman from DRI and Wendy Calvin from the University of Nevada, Reno.

The full paper, “Four-fold increase in solar forcing on snow in western U.S. burned forests since 1999,” is available here.

Cristina Rojas of PSU’s College of Liberal Arts and Sciences contributed to this release.

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The Desert Research Institute (DRI) is a recognized world leader in basic and applied interdisciplinary research. Committed to scientific excellence and integrity, DRI faculty, students, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge, supported Nevada’s diversifying economy, provided science-based educational opportunities, and informed policy makers, business leaders, and community members. With campuses in Reno and Las Vegas, DRI is one of eight institutions in the Nevada System of Higher Education.

As Oregon’s only urban public research university, Portland State offers tremendous opportunity to 27,000 students from all backgrounds. Our mission to “Let Knowledge Serve the City” reflects our dedication to finding creative, sustainable solutions to local and global problems. Our location in the heart of Portland, one of America’s most dynamic cities, gives our students unmatched access to career connections and an internationally acclaimed culture scene. “U.S. News & World Report” ranks us among the nation’s most innovative universities.

First non-polar historical iodine record shows impact of fossil fuel emissions

First non-polar historical iodine record shows impact of fossil fuel emissions

Reno, Nev. (Nov. 13, 2018): A new ice core record from the French Alps shows impacts of fossil fuel emissions in the form of a steep increase in iodine levels during the second half of the 20th century, according to a study released this week by an international team of scientists from the Université Grenoble Alpes-CNRS of France, the Desert Research Institute (DRI) in Reno, Nev., and the University of York in England.

“Model and laboratory studies had suggested that atmospheric iodine should have increased during recent decades as a result of increasing fossil fuel emissions but few long-term records of iodine existed with which to test these model findings, and none in Western Europe where modeled iodine increases were especially pronounced,” said French researcher and lead author Michel Legrand, Ph.D.

Iodine is an important nutrient for human health, key in the formation of thyroid hormones. It is present in ocean waters, and is released into the atmosphere when Iodide (I-) reacts with ozone (03) at the water’s surface. From the atmosphere, iodine is deposited onto Earth’s land surfaces, and absorbed by humans in the foods that we eat.

The new study, published in the Proceedings of the National Academy of Sciences, was initiated after scientists observed a three-fold increase in iodine between 1950 and the 1990s measured in an ice core from the Col du Dome region of France. The core was collected by French scientists and analyzed in 2017 in DRI’s Ultra Trace Ice Core Analysis Laboratory.

 

Researchers examine an ice core sample drilled from Mont Blanc.

Researchers examine an ice core sample drilled from Mont Blanc. Credit: B. Jourdain, L’Institut des Géosciences de l’Environnement.

Although previous modeling simulations had indicated a similar increase in global iodine emissions during the 20th century, this new record provides the first ice core iodine record from outside of the polar regions.

“Iodine has been measured previously in polar ice cores but changes there largely can be attributed to variations in sea ice,” said Joe McConnell, Ph.D., research professor of hydrology and head of DRI’s ice core laboratory. “These variations mask the larger scale trends linked to fossil fuel emissions and changes in ozone chemistry. Our new iodine record extends from 1890 to 2000 and is from the French Alps, a part of the world where there are no sea ice influences.”

As part of this study, more than 120 meters (nearly 400 feet) of ice core from the French Alps was analyzed for iodine and a broad range of chemical species by a group of DRI researchers that included McConnell, Monica Arienzo, Ph.D., Nathan Chellman, and Kelly Gleason, Ph.D., using DRI’s unique continuous analytical system.

The study team then analyzed the ice core record alongside modeling simulations to investigate past atmospheric iodine concentrations and changes in iodine deposition across Europe. According to their results, the observed tripling of iodine levels in the ice during the 1950s to 1990s were caused by increased iodine emissions from the ocean.

An ice core sample is processed in DRI’s Ultra-Trace Ice Core Laboratory in Reno, Nev.

An ice core sample is processed in DRI’s Ultra-Trace Ice Core Laboratory in Reno, Nev. Credit: Joe McConnell/DRI.

Ozone in the lower atmosphere acts as an air pollutant and greenhouse gas. Because iodine emissions from the ocean occur when iodine in the water reacts with ozone in the lower atmosphere, the study results indicate that increased ozone levels are increasing the availability of iodine in the atmosphere – and also that iodine is helping to destroy this “bad” ozone.

“Iodine’s role in human health has been recognized for some time – it is an essential part of our diets,” said Lucy Carpenter, Ph.D., Professor with University of York’s Department of Chemistry. “Its role in climate change and air pollution, however, has only been recognized recently and the impact of iodine in the atmosphere is not currently a feature of the climate or air quality models that predict future global environmental changes.”

According to the World Health Organization, iodine deficiency remains a significant health problem in parts of Europe, including France, Italy and certain regions of Spain – regions that now appear to have received a boost in iodine levels in recent years.

“The silver lining in the findings of this study is that the increase in human-caused pollution during the latter half of the 20th century may be leading to an increase in the availability of iodine as an essential nutrient,” Legrand said.

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To view the study, titled Alpine ice evidence of a three-fold increase in atmospheric iodine deposition since 1950 in Europe due to increasing oceanic emissions, published in the journal Proceedings of the National Academy of Sciences on 12 November 2018, please visit:  http://www.pnas.org/content/early/2018/11/07/1809867115

Samantha Martin from the University of York contributed to this release.

The Desert Research Institute (DRI) is a recognized world leader in basic and applied interdisciplinary research. Committed to scientific excellence and integrity, DRI faculty, students, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge, supported Nevada’s diversifying economy, provided science-based educational opportunities, and informed policy makers, business leaders, and community members. With campuses in Reno and Las Vegas, DRI serves as the non-profit research arm of the Nevada System of Higher Education. Learn more at dri.edu, and connect with us on social media on Facebook, Instagram and Twitter