May 28, 2021 | News releases, Research findings
DRI Ice Core Lab Data Shows Magnitude of Historic Fire Activity in Southern Hemisphere
Ice Cores
Fire Activity
Climate Change
Above: Smoke from human-caused wildfires on the Patagonian steppe are trapped in Antarctic ice.
Credit: Kathy Kasic/Brett Kuxhausen, Montana State University.
A new study in Science Advances features ice core data from the DRI Ice Core Laboratory and research by Nathan Chellman, Ph.D., Monica Arienzo, Ph.D., and Joe McConnell, Ph.D.
Fire emissions in the Southern Hemisphere may have been much higher during pre-industrial times than in the present day, according to new research from an international team of scientists including Nathan Chellman, Ph.D., Monica Arienzo, Ph.D., and Joe McConnell, Ph.D., of the Desert Research Institute (DRI) in Reno.
The study, published today in Science Advances, used new ice core data from DRI’s Ice Core Laboratory to document changes in levels of soot from ancient fires and modern fossil fuel combustion during the years 1750 to 2000. Many of the 14 Antarctic ice cores included in the study were obtained through national and international collaborations, and together comprise an unprecedented long-term record of Southern Hemisphere fire activity that provided the foundation for the modeling effort described in the new paper.
All of the ice cores were analyzed using a specialized method for soot measurements in ice that McConnell and his team pioneered at DRI nearly 15 years ago. This method is now widely used in laboratories around the world.
For more information about the DRI Ice Core Laboratory, please visit: https://www.dri.edu/labs/trace-chemistry-laboratory/. The full news release from Harvard University, A fiery past sheds new light on the future of global climate change, is posted below.
Co-author Dr. Robert Mulvaney from the British Antarctic Arctic Survey drilling the James Ross Island core in the Antarctic Peninsula.
The full text of the paper, Improved estimates of preindustrial biomass burning reduce the magnitude of aerosol climate forcing in the Southern Hemisphere, is available from Science Advances: https://advances.sciencemag.org/content/7/22/eabc1379.abstract
A fiery past sheds new light on the future of global climate change
Ice core samples reveal significant smoke aerosols in the pre-industrial Southern Hemisphere
By Leah Burrows, Harvard University
Centuries-old smoke particles preserved in the ice reveal a fiery past in the Southern Hemisphere and shed new light on the future impacts of global climate change, according to new research published in Science Advances.
“Up till now, the magnitude of past fire activity, and thus the amount of smoke in the preindustrial atmosphere, has not been well characterized,” said Pengfei Liu, a former graduate student and postdoctoral fellow at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and first author of the paper. “These results have importance for understanding the evolution of climate change from the 1750s until today, and for predicting future climate.”
One of the biggest uncertainties when it comes to predicting the future impacts of climate change is how fast surface temperatures will rise in response to increases in greenhouse gases. Predicting these temperatures is complicated since it involves the calculation of competing warming and cooling effects in the atmosphere. Greenhouse gases trap heat and warm the planet’s surface while aerosol particles in the atmosphere from volcanoes, fires and other combustion cool the planet by blocking sunlight or seeding cloud cover. Understanding how sensitive surface temperature is to each of these effects and how they interact is critical to predicting the future impact of climate change.
Ancient ice from James Ross Island in the Northern Antarctic Peninsula about to be extracted from the drill barrel.
Many of today’s climate models rely on past levels of greenhouse gasses and aerosols to validate their predictions for the future. But there’s a problem: While pre-industrial levels of greenhouse gasses are well documented, the amount of smoke aerosols in the preindustrial atmosphere is not.
To model smoke in the pre-industrial Southern Hemisphere, the research team looked to Antarctica, where the ice trapped smoke particles emitted from fires in Australia, Africa and South America. Ice core scientists and co-authors of the study, Joseph McConnell and Nathan Chellman from the Desert Research Institute in Nevada, measured soot, a key component of smoke, deposited in an array of 14 ice cores from across the continent, many provided by international collaborators.
“Soot deposited in glacier ice directly reflects past atmospheric concentrations so well-dated ice cores provide the most reliable long-term records,” said McConnell.
What they found was unexpected.
“While most studies have assumed less fire took place in the preindustrial era, the ice cores suggested a much fierier past, at least in the Southern Hemisphere,” said Loretta Mickley, Senior Research Fellow in Chemistry-Climate Interactions at SEAS and senior author of the paper.
To account for these levels of smoke, the researchers ran computer simulations that account for both wildfires and the burning practices of indigenous people.
“The computer simulations of fire show that the atmosphere of the Southern Hemisphere could have been very smoky in the century before the Industrial Revolution. Soot concentrations in the atmosphere were up to four times greater than previous studies suggested. Most of this was caused by widespread and regular burning practiced by indigenous peoples in the pre-colonial period,” said Jed Kaplan, Associate Professor at the University of Hong Kong and co-author of the study.
Drilling ice cores in East Antarctica as part of the Norwegian-U.S. International IPY Scientific Traverse of East Antarctica.
This result agrees with the ice core records that also show that soot was abundant before the start of the industrial era and has remained relatively constant through the 20th century. The modeling suggests that as land-use changes decreased fire activity, emissions from industry increased.
What does this finding mean for future surface temperatures?
By underestimating the cooling effect of smoke particles in the pre-industrial world, climate models might have overestimated the warming effect of carbon dioxide and other greenhouse gasses in order to account for the observed increases in surface temperatures.
“Climate scientists have known that the most recent generation of climate models have been over-estimating surface temperature sensitivity to greenhouse gasses, but we haven’t known why or by how much,” said Liu. “This research offers a possible explanation.”
“Clearly the world is warming but the key question is how fast will it warm as greenhouse gas emissions continue to rise. This research allows us to refine our predictions moving forward,” said Mickley.
The research was co-authored by Yang Li, Monica Arienzo, John Kodros, Jeffrey Pierce, Michael Sigl, Johannes Freitag, Robert Mulvaney, and Mark Curran.
It was funded by the National Science Foundation’s Geosciences Directorate under grants AGS-1702814 and 1702830, with additional support from 0538416, 0538427, and 0839093.
Additional Information:
The full text of the paper, Improved estimates of preindustrial biomass burning reduce the magnitude of aerosol climate forcing in the Southern Hemisphere, is available from Science Advances: https://advances.sciencemag.org/content/7/22/eabc1379.abstract
The news release above was reposted with permission from Harvard University: https://www.seas.harvard.edu/news/2021/05/fiery-past-sheds-new-light-future-global-climate-change.
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About the Desert Research Institute
The Desert Research Institute (DRI) is a recognized world leader in basic and applied environmental 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 policymakers, 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. For more information, please visit www.dri.edu
Nov 28, 2018 | News releases, Research findings
Reno, Nev. (Nov. 28, 2018): This week, new research on historical climate changes in the Earth’s polar regions by an international team of scientists was published in the journal Nature. The study, titled “Abrupt Ice Age Shifts in Southern Westerlies and Antarctic Climate Forced from the North,” is underpinned by data provided by Joe McConnell, Ph.D., director of DRI’s Ultra-Trace Chemistry Laboratory in Reno, Nev.
The recently published study explains the interconnection between Arctic and Antarctic climates, tracing how strong currents in the North Atlantic during the Ice Age forced Southern Hemisphere climate on two different timescales: first, by rapidly warming Greenland and triggering immediate atmospheric changes in Antarctica due to shifting wind patterns, and second, by cooling the continent via colder ocean temperatures two centuries later. Researchers liken the atmospheric climate change in the North Atlantic to a “text message,” delivered immediately to the Southern Hemisphere, while the oceanic cooling is more like a “postcard,” not felt in Antarctica for another 200 years.
To identify this climate “teleconnection” between Earth’s poles, researchers relied on detailed chemical analyses of more than 1.5 km of Antarctic ice core, including more than 400,000 individual measurements, made in the Ultra-Trace Chemistry Laboratory using a unique continuous flow system and inductively coupled plasma mass spectrometry. Retrieved from the West Antarctic Ice Sheet (WAIS), this ice core sample, known as the WAIS Divide core, was collected by a team including DRI emeritus research professor Kendrick Taylor, Ph.D. Their original research into the connection between the Earth’s polar regions using the WAIS Divide core was first explained in Nature in 2015.
The full text of the study titled “Abrupt ice-age shifts in southern westerly winds and Antarctic climate forced from the north” is available in Nature: https://www.nature.com/articles/s41586-018-0727-5. A full news release from Oregon State University is below.
Continue Reading DRI ice core data illustrates climate “teleconnection” between Earth’s poles during climate changes in the last Ice Age
Oct 3, 2018 | Blog, Featured researchers
Henry Sun, Ph.D., is an associate research professor of microbiology with the Division of Earth and Ecosystem Sciences at the Desert Research Institute in Las Vegas. Henry specializes in the study of microscopic organisms that live in extreme environments, often using specimens from here on earth to learn about possibilities for life on Mars. He is originally from China and has a bachelor’s degree in botany and master’s degree in phycology (the study of algae) from Nanjing University. He also holds a Ph.D. in microbiology from Florida State University and completed a post-doc in astrobiology (the study of life in the universe) at the Jet Propulsion Lab in Pasadena, CA. Henry has been a member of the DRI community since 2004. In his free time, he enjoys playing pickup basketball with friends in Las Vegas, and spending time with his wife and two kids.
DRI: What do you do here at DRI?HS: I do quite a few things, all centered around the study of life in extreme environments – places that are in one way or another similar to Mars. We are studying what we call analog environments, trying to understand whether there’s life in these places that are comparable to Mars, learning how to go about detecting life and organisms, and developing ideas for reliable instruments that we can send to Mars to look for life there.
DRI: How did you become interested in this line of work?
HS: It started in graduate school, when I was given the opportunity to go to Antarctica, to a place called the Dry Valleys, to do my dissertation work. Until 1976, this was a place thought to be devoid of all life. But my former adviser, Imre Friedmann, extrapolating from his work in the hot deserts in the southwestern U.S., discovered thriving communities of microalgae and cyanobacteria in the pore spaces in the Antarctic sandstone. Sandstone is translucent, so sunlight can penetrate the first few millimeters. The stone holds onto water in the pore spaces so it doesn’t dry out right away. And that’s all you need to support life. I fell in love with these organisms on my very first trip there.
Henry Sun at work in Antarctica, January 2005.
DRI: What did you learn from studying those organisms?
HS: Probably the most remarkable thing we have learned about these organisms is that they have a very slow growth rate. We have monitored a few rocks closely over the last 50 years and never saw any appreciable signs of growth. In fact, they are so long-lived that their age can be determined by radiocarbon decay. In other words, if you look at their radiocarbon content, you would think they are dead, fossilized organisms. But we know they are alive because as soon as we thaw them to a normal temperature they start to breathe, taking up carbon dioxide and releasing oxygen. And because they start to grow and reproduce when we put them in a petri dish and incubate at more favorable temperature conditions.
That said, we still have a lot to learn about these organisms, and the opportunity for a serious study presented itself this year. When my former advisor passed away in 2007, he left behind a large collection of thousands of rocks from Antarctica, amassed over his career, in a walk-in -30oC freezer at Florida State University in Tallahassee, Florida. Last year, Florida State decided to decommission that building, and the samples were about to be thrown out. This past June, with a little help from DRI and NASA, we raised some money and purchased three freezers. I drove to Florida and hauled all of the samples back in a cargo van full of coolers and dry ice. I moved the entire collection to Las Vegas without them ever being thawed, so now they are sitting at DRI waiting to be studied.
An outcrop of Antarctic sandstone at one of Henry Sun’s field sites.
DRI: What are you planning to do with these samples?
HS: Inside of the freezers, the samples are kept at temperatures of -30oC (-22oF) and in complete darkness, but the microbes are still alive. As I said, we have thousands of samples. Only two samples have been studied using modern-day DNA analysis. So, the first thing we want to is a comprehensive molecular study and find out what lives in these samples.
We are also working with colleagues at the NASA Ames Research Center to look for cyanobacteria that can grow not using the visible light, but using the infrared. Visible light, which photosynthetic organisms prefer, is filtered out by the sandstone. But the infrared is still present. It is not as good as the visible, but that is all the organisms at the bottom of the colonized zone have. We speculate that they may subsist on the infrared.
Closeup of one of Henry Sun’s Antarctic rock samples, home to unknown species of microorganisms.
DRI: What do you like best about what you do?
HS: I feel most rewarded when we engage school teachers and their students in what we do. We do this through a program called Spaceward Bound, which was created by Chris McKay, DRI’s Nevada Medalist from two years ago. The goal is to train the next generation of space explorers in remote but scientifically interesting places that are analogous to the moon or Mars. The reason why we need to start this now is because the first human mission to Mars may happen as early as the 2030s. The scientists who will go to Mars to study its environment are still in school today. We have done several Spaceward Bound expeditions in the Mojave and Death Valley area with teachers and students from Nevada. To me, there is no greater reward than to see children get inspired by the work we do so that one day they may become scientists themselves and continue to push back the frontier of knowledge.
Henry Sun talks with a student at DRI’s 2018 ‘May Science Be With You’ event in Las Vegas.
For more information on Henry Sun and his research, continue to his research page: https://www.dri.edu/directory/henry-sun
Sep 20, 2018 | News releases, Research findings
Above: A lone researcher is silhouetted by the summer sun, low in the Antarctic sky. Credit: Bradley Markle, UCSB.
Reno, Nev. (Sept. 20, 2018) – In September, new research by a team from the University of California, Santa Barbara, the University of Washington, Columbia University, and the Desert Research Institute (DRI) was published in the journal Nature Geoscience. The study, titled Concomitant variability in high-latitude aerosols, water isotopes and the hydrologic cycle, utilized data provided by Joe McConnell, Ph.D., director of DRI’s Ultra-Trace Chemistry Laboratory in Reno, Nev.
The study explains an observed connection between concentrations of aerosols (small atmospheric particles such as mineral dust and sea-salt) and the ratios of different isotopes of water (variant forms of H20 in which the atoms carry extra neutrons) found in Antarctic ice cores.
Aerosol measurements for this study, which consisted of more than 500,000 measurements of calcium and sodium in 2.1 kilometers (1.3 miles) of Antarctic ice, were made in the Ultra-Trace Chemistry Laboratory using a unique continuous flow system and inductively coupled plasma mass spectrometry. Parts of these aerosol records have been published previously, but they are published in full in the new study. The full news release from U.C. Santa Barbara is below.
These shallow cores help us with the interpretation of the deep one,” explained UC Santa Barbara’s Bradley Markle. Credit: Bradley Markle, UCSB.
Dust, Rain and the Poles
Warmer climates will likely decrease the amount of airborne sediments reaching the poles
By Harrison Tasoff, University of California, Santa Barbara
Every year, the global climate transports billions of tons of dust around the world. These aerosols play a key role in many of Earth’s geological and biological cycles.
For instance, wind blows millions of tons of dust from the Sahara Desert across the Atlantic Ocean, where it fertilizes the Amazon Rainforest. The collective action of billions of trees pumping water from the ground then generates its own weather pattern, affecting the whole of South America.
When climate scientist Bradley Markle, at UC Santa Barbara’s Earth Research Institute, spotted a correlation between the ratios of heavy molecules and the concentration of particulate matter in the Antarctic ice cores he was studying, he immediately set out to uncover the deeper connection. His findings appear in the journal Nature Geoscience.
For decades scientists have been puzzled by the relationship between aerosol concentrations and the ratios of different molecules of water in ice cores, and Markle appears to have finally found the connection. His research increases our understanding of the processes at work in Earth’s atmosphere and could help to improve our climate models.
Markle focuses on understanding how climactic processes concentrate atoms of different weights in certain areas. Consider oxygen, for example. Every oxygen atom has eight positively charged protons. That’s what makes it oxygen. However, the number of neutrally charged neutrons it contains can vary from eight to 10. And the greater the number of neutrons, the heavier the isotope.
Water has one oxygen atom bonded to two hydrogen atoms, so water containing lighter isotopes, like 16O — which has eight neutrons — weighs less than water with heavier ones, like 18O — which has 10. Certain processes affect heavier molecules more than their lighter counterparts, leading to varying distributions of different weights across the globe. So even though 99.7 percent of oxygen on Earth is 16O, slight differences in the ratio between 16O and 18O provide scientists with valuable clues about the planet’s climate. In fact, measurements of these ratios in ice cores underlie our most detailed long records of Earth’s temperature history, Markle explained. They span hundreds of thousands of years before humans started measuring temperature directly.
Researchers examine the ice cores, which are backlit by the sun. Credit: Bradley Markle, UCSB.
Scientists noticed that ice layers with higher ratios of heavy isotopes also contained a greater concentration of trapped aerosols. “And it’s a very unique relationship, too,” Markle said. “It’s very clearly logarithmic … so it seems like it needs a strong, logarithmic process to account for it.
“The correlation between the thing that records the climate (the water isotope ratios) and these aerosols is extremely good,” he continued. “Better than you get in almost anything else in this field.”
Precipitation has the most influence on the percentage of heavy isotopes that make it to high latitudes, since heavier water molecules condense more readily compared to light ones, Markle explained. Warm air holds more moisture than cold air, so as it cools on its way toward the poles, the moisture condenses and preferentially loses the heavier molecules. If the poles become warmer, the air will not cool as much, so a greater number of heavy molecules will make it to higher latitudes. As a result, scientists associate low ratios of heavy isotopes with colder periods in Earth’s history.
Scientists suspected that these climatic conditions impacted the locations these aerosols came from, somehow effecting greater emissions during cooled periods than warm ones. However, years of research had yet to produce a model that fit the data. In addition, source variability is challenging to investigate because it requires looking at myriad factors in many different places. “People have investigated it, and they can’t get the sources to have such large changes in aerosol emissions,” Markle said.
Markle compared aerosol data from the Antarctic ice cores with similarly aged seafloor sediment from the oceans just below South America, which is the dominant source of the airborne dust found in Antarctica. He discovered that aerosol levels in the ocean sediment increased three- to six-fold during the last glacial maximum. However, concentrations in the ice cores soared to levels 20 to 100 times baseline rates. Clearly most of the change seen in the ice cores must be due to factors far from the source of the aerosols.
Then Markle recognized a similarity between the isotope ratios and the aerosol concentrations: The physics of moisture in the atmosphere is driving both of them.
A view of the Antarctic coast from the Southern Ocean. Credit: Bradley Markle, UCSB.
Without aerosols, the world would have no rain. Water vapor needs a surface to condense, or form droplets. This could be a steamy shower window or a fleck of dust floating high in the clouds. In this way, precipitation washes the sky of aerosols. More precipitation between the source of the aerosols and the poles means lower concentrations of aerosols make it to the glaciers, and thus into the ice cores. And more precipitation also leads to lower ratios of heavy isotopes. Markle had discovered the connection.
What’s more, the scouring effect precipitation has on aerosols is exponential, meaning its influence increases the longer, and farther, the aerosols travel from their source. Precisely the sort of relationship Markle needed to match the data.
“This rainout theory ends up solving a whole bunch of things at once,” Markle said. It clarifies the correlation between aerosol concentrations and water isotopes, as well as the greater variability in aerosol levels at the poles than in locations closer to the source of the debris. The effect also explains why dust levels vary more than sea salt levels in the aerosol record: The ocean is closer to Antarctica than the source of dust, so precipitation has less impact on the amount of sea salt that makes it to the West Antarctic ice-sheet.
Markle is cautious about making predictions for our current climate change. “The effect that we saw in the ice cores was a really big effect, but it’s a big effect on multicentury, multimillennium time scales,” Markle said. Other sources of variability may be more prominent over shorter timeframes, he explained.
Nonetheless, warming temperatures would forecast decreasing concentrations of aerosols reaching the Arctic and Antarctic. Since aerosols reflect heat and sunlight, this could exacerbate warming trends over long periods of time. Changes in aerosol distribution could also affect the ocean, since they also contain nutrients and minerals vital to ocean’s food web.
Markle plans to leverage his newfound understanding of these relationships to investigate changes not only in the strength of hydrologic cycle but also in its spatial pattern. “Because the hydrologic cycle is tied to Earth’s temperature gradients, I think we can use these records to understand changes in polar amplification,” he explained. This is the phenomenon where the poles warm more than lower latitudes during climate change.
“This is a big deal in modern climate change,” he added, “and understanding how it has happened in the past would be extremely useful.”
This news release was originally published by the University of California, Santa Barbara. To view the original story, please visit: http://www.news.ucsb.edu/2018/019185/dust-rain-and-poles
To view the study titled Concomitant variability in high-latitude aerosols, water isotopes and the hydrologic cycle, published in Nature Geoscience on 10 September 2018, please visit: https://www.nature.com/articles/s41561-018-0210-9
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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 serves as the non-profit research arm of the Nevada System of Higher Education. For more information, please visit www.dri.edu.
Sep 5, 2017 | News releases, Research findings
Above: A 15-meter pan-sharpened Landsat 8 image of the Mount Takahe volcano rising more than 2,000 meters (1.2 miles) above the surrounding West Antarctic ice sheet in Marie Byrd Land, West Antarctica. Credit: Landsat Image Mosaic of Antarctica (LIMA). USGS and NASA, LIMA Viewer, https://lima.gsfc.nasa.gov/. Image Date: March 4, 2015
New findings explain synchronous deglaciation that occurred 17,700 Years Ago
Reno, NV (Sept. 5, 2017) – New findings published today in the Proceedings of the National Academy of Sciences of the United States of America (PNAS) by Desert Research Institute (DRI) Professor Joseph R. McConnell, Ph.D., and colleagues document a 192-year series of volcanic eruptions in Antarctica that coincided with accelerated deglaciation about 17,700 years ago.
“Detailed chemical measurements in Antarctic ice cores show that massive, halogen-rich eruptions from the West Antarctic Mt. Takahe volcano coincided exactly with the onset of the most rapid, widespread climate change in the Southern Hemisphere during the end of the last ice age and the start of increasing global greenhouse gas concentrations,” according to McConnell, who leads DRI’s ultra-trace chemical ice core analytical laboratory.
Climate changes that began ~17,700 years ago included a sudden poleward shift in westerly winds encircling Antarctica with corresponding changes in sea ice extent, ocean circulation, and ventilation of the deep ocean. Evidence of these changes is found in many parts of the Southern Hemisphere and in different paleoclimate archives, but what prompted these changes has remained largely unexplained.
“We know that rapid climate change at this time was primed by changes in solar insolation and the Northern Hemisphere ice sheets,” explained McConnell. “Glacial and interglacial cycles are driven by the sun and Earth orbital parameters that impact solar insolation (intensity of the sun’s rays) as well as by changes in the continental ice sheets and greenhouse gas concentrations.”
“We postulate that these halogen-rich eruptions created a stratospheric ozone hole over Antarctica that, analogous to the modern ozone hole, led to large-scale changes in atmospheric circulation and hydroclimate throughout the Southern Hemisphere,” he added. “Although the climate system already was primed for the switch, we argue that these changes initiated the shift from a largely glacial to a largely interglacial climate state. The probability that this was just a coincidence is negligible.”
Furthermore, the fallout from these eruptions – containing elevated levels of hydrofluoric acid and toxic heavy metals – extended at least 2,800 kilometers from Mt. Takahe and likely reached southern South America.
Monica Arienzo, Ph.D., an assistant research professor of hydrology at DRI, loads an 18,000-year-old sample of the WAIS Divide ice core for continuous chemical analysis using DRI’s ultra-trace ice core analytical system in Reno, Nevada. Credit: DRI Professor Joseph R. McConnell, Ph.D.
How Were These Massive Antarctic Volcanic Eruptions Discovered and Verified?
McConnell’s ice core laboratory enables high-resolution measurements of ice cores extracted from remote regions of the Earth, such as Greenland and Antarctica. One such ice core, known as the West Antarctic Ice Sheet Divide (WAIS Divide) core was drilled to a depth of more than two miles (3,405 meters), and much of it was analyzed in the DRI Ultra-Trace Laboratory for more than 30 different elements and chemical species.
Additional analyses and modeling studies critical to support the authors’ findings were made by collaborating institutions around the U.S. and world.
“These precise, high-resolution records illustrate that the chemical anomaly observed in the WAIS Divide ice core was the result of a series of eruptions of Mt. Takahe located 350 kilometers to the north,” explained Monica Arienzo, Ph.D., an assistant research professor of hydrology at DRI who runs the mass spectrometers that enable measurement of these elements to as low as parts per quadrillion (the equivalent of 1 gram in 1,000,000,000,000,000 grams).
“No other such long-lasting record was found in the 68,000-year WAIS Divide record,” notes Michael Sigl, Ph.D., who first observed the anomaly during chemical analysis of the core. “Imagine the environmental, societal, and economic impacts if a series of modern explosive eruptions persisted for four or five generations in the lower latitudes or in the Northern Hemisphere where most of us live!”
Discovery of this unique event in the WAIS Divide record was not the first indication of a chemical anomaly occurring ~17,700 years ago.
“The anomaly was detected in much more limited measurements of the Byrd ice core in the 1990s,” notes McConnell, “but exactly what it was or what created it wasn’t clear. Most previous Antarctic ice core records have not included many of the elements and chemical species that we study, such as heavy metals and rare earth elements, that characterize the anomaly – so in many ways these other studies were blind to the Mt. Takahe event.”
DRI’s initial findings were confirmed by analysis of replicate samples from WAIS Divide, producing nearly identical results.
“We also found the chemical anomaly in ice from two other Antarctic ice cores including archived samples from the Byrd Core available from the University of Copenhagen and ice from Taylor Glacier in the Antarctic Dry Valleys,” said Nathan Chellman, a graduate student working in McConnell’s laboratory.
Extraction of the WAIS-Divide ice core and analysis in DRI’s laboratory were funded by the U.S. National Science Foundation (NSF).
“The WAIS Divide ice core allows us to identify each of the past 30,000 years of snowfall in individual layers of ice, thus enabling detailed examination of conditions during deglaciation,” said Paul Cutler, NSF Polar Programs’ glaciology program manager. “The value of the WAIS Divide core as a high-resolution climate record is clear in these latest results and is another reward for the eight-year effort to obtain it.”
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The Desert Research Institute (DRI) is a recognized world leader in investigating the effects of natural and human-induced environmental change and advancing technologies aimed at assessing a changing planet. For more than 50 years DRI research faculty, students, and staff have applied scientific understanding to support the effective management of natural resources while meeting Nevada’s needs for economic diversification and science-based educational opportunities. With campuses in Reno and Las Vegas, DRI serves as the non-profit environmental research arm of the Nevada System of Higher Education. For more information, please visit www.dri.edu.
Aug 10, 2017 | News releases, Research findings
Monica Arienzo, PhD, assistant research professor of hydrology at DRI, demonstrates part of the black carbon analysis process in the clean room of DRI’s Ice Core Laboratory. Credit DRI.
DRI-led research team publishes longest ice core black carbon record to date
Reno, NV (Aug. 10, 2017): Smoky skies and burnt landscapes are the easily recognizable, local and immediate impacts of large wildfires. Long after these fires are gone, their emissions are cataloged and stored forever in ice covering the Earth’s polar regions.
New research, led by a team at the Desert Research Institute (DRI) in Reno, Nevada, has revealed that Earth’s ancient climate conditions affected large regional scale wildfires.
The new study identifies a link between the concentration of wildfire black carbon (BC) emissions —a type of biomass-burning aerosol particle commonly known as soot—found in Antarctic ice cores and climate conditions in the Southern Hemisphere during the mid-Holocene, about 6,000 years ago.
Led by Monica Arienzo, PhD, an assistant research professor of hydrology at DRI, a team of international researchers used DRI’s unique ultra-trace ice core analytical laboratory to measure BC concentrations in two Antarctic ice cores, ice that contains traces of compounds present in the atmosphere at the time the snow fell. This method allowed researchers to make comparisons to other records, such as lake and marine sediment cores, and develop a high-resolution record of biomass-burning emissions in the Southern Hemisphere from 14 to 2.5 thousand years before present day.
“This is the longest ice core black carbon record published to date,” Arienzo said, “and it tells us a fascinating story about wildfire.”
The new ice core record illustrates that, during the mid-Holocene, decreases in precipitation and soil moisture coupled with increases in temperature and fire season length in regions of South America were mirrored by increased concentrations of BC in Antarctic ice.
“Our analysis gives us a sense of what climate-fire relationships were like before significant human-caused changes to the climate,” explained Joe McConnell, PhD, a study co-author and research professor of hydrology at DRI. “Knowing what climate-fire relationships were like in the past will help scientists make more accurate climate models because they can account for BC contributions from wildfires in addition to those from human sources.”
BC acts as an agent of climate forcing, a process which occurs in the atmosphere when the amount of incoming energy is greater than the amount of outgoing energy, “forcing” the planet to adjust by releasing energy as heat and warming up. This is a natural process, catalyzed by events such as large volcanic eruptions and changes in the sun’s energy output; however, human-caused climate forcing in the form of BC emissions, has increased dramatically since the Industrial Revolution and now is a significant climate forcing agent, second only to carbon dioxide (CO2).
BC also impacts ice sheet albedo, the reflectivity of a surface. Ice and snow have a high albedo because they are very white and reflect much of the sun’s energy. This reflectivity keeps the snow and ice cold and delays melting. Conversely, snow and ice with BC deposits have a lower albedo, causing increased absorption of energy into the snow and ice and more rapid melting.
“Recent precipitation models indicate vast regional changes in rainfall in the Southern Hemisphere in the future,” Arienzo added. “Our findings indicate that such rainfall changes may be accompanied by changes in Southern Hemisphere wildfires. Given that BC emissions from human sources are predicted to increase, our findings are an important factor for climate predictions involving BC impacts.”
The full version of the study—“Holocene black carbon in Antarctica paralleled Southern Hemisphere climate”—is available online at – http://onlinelibrary.wiley.com/doi/10.1002/2017JD026599/full
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The Desert Research Institute (DRI) is a recognized world leader in investigating the effects of natural and human-induced environmental change and advancing technologies aimed at assessing a changing planet. For more than 50 years DRI research faculty, students, and staff have applied scientific understanding to support the effective management of natural resources while meeting Nevada’s needs for economic diversification and science-based educational opportunities. With campuses in Reno and Las Vegas, DRI serves as the non-profit environmental research arm of the Nevada System of Higher Education. For more information, please visit www.dri.edu.
