Jun 1, 2022 | Blog, Featured researchers
Field Notes From a DRI Research Team in Greenland: A Story Map
In May 2022, a team led by scientists from DRI in Reno, Nevada departed for Greenland, where they were joined by ice drilling, Arctic logistics, and mountaineering experts. Together, the team plans to collect a 440 meter-long ice core that will represent 4,000 years of Earth and human history.
For much of their time on the Greenland ice sheet, the team will not have access to the internet or phone service — but they are able to send short text messages back to DRI from a Garmin inReach two-way satellite communicator. You can follow along with their journey on our Story Map, “The Return to Tunu.”
Oct 6, 2021 | News releases, Research findings
Early Human Activities Impacted Earth’s Atmosphere More Than Previously Known
Oct 6, 2021
RENO, NV
By Kelsey Fitzgerald
Climate Change
Earth’s Atmosphere
Ice Cores
Above: After a storm at the drilling camp on James Ross Island, northern Antarctic Peninsula.
New study links an increase in black carbon in Antarctic ice cores to Māori burning practices in New Zealand more than 700 years ago
The James Ross Island core drilled to bedrock in 2008 by the British Antarctic Survey provided an unprecedented record of soot deposition in the northern Antarctic Peninsula during the past 2000 years and revealed the surprising impacts of Māori burning in New Zealand starting in the late 13th century. Robert Mulvaney, Ph.D., pictured here led collection of the core.
Reno, Nev. (October 6, 2021) – Several years ago, while analyzing ice core samples from Antarctica’s James Ross Island, scientists Joe McConnell, Ph.D., and Nathan Chellman, Ph.D., from DRI, and Robert Mulvaney, Ph.D., from the British Antarctic Survey noticed something unusual: a substantial increase in levels of black carbon that began around the year 1300 and continued to the modern day.
Black carbon, commonly referred to as soot, is a light-absorbing particle that comes from combustion sources such as biomass burning (e.g. forest fires) and, more recently, fossil fuel combustion. Working in collaboration with an international team of scientists from the United Kingdom, Austria, Norway, Germany, Australia, Argentina, and the U.S., McConnell, Chellman, and Mulvaney set out to uncover the origins of the unexpected increase in black carbon captured in the Antarctic ice.
The team’s findings, which published this week in Nature, point to an unlikely source: ancient Māori land-burning practices in New Zealand, conducted at a scale that impacted the earth’s atmosphere across much of the Southern Hemisphere and dwarfed other preindustrial emissions in the region during the past 2,000 years.
“The idea that humans at this time in history caused such a significant change in atmospheric black carbon through their land clearing activities is quite surprising,” said McConnell, research professor of hydrology at DRI who designed and led the study. “We used to think that if you went back a few hundred years you’d be looking at a pristine, pre-industrial world, but it’s clear from this study that humans have been impacting the environment over the Southern Ocean and the Antarctica Peninsula for at least the last 700 years.”
Four ice cores from continental Antarctica were drilled in East Antarctica, including two as part of the Norwegian-American International Polar Year Antarctic Scientific Traverse.
Tracing the black carbon to its source
To identify the source of the black carbon, the study team analyzed an array of six ice cores collected from James Ross Island and continental Antarctica using DRI’s unique continuous ice-core analytical system. The method used to analyze black carbon in ice was first developed in McConnell’s lab in 2007.
While the ice core from James Ross Island showed a notable increase in black carbon beginning around the year 1300, with levels tripling over the 700 years that followed and peaking during the 16th and 17th centuries, black carbon levels at sites in continental Antarctica during the same period of time stayed relatively stable.
Andreas Stohl, Ph.D., of the University of Vienna led atmospheric model simulations of the transport and deposition of black carbon around the Southern Hemisphere that supported the findings.
“From our models and the deposition pattern over Antarctica seen in the ice, it is clear that Patagonia, Tasmania, and New Zealand were the most likely points of origin of the increased black carbon emissions starting about 1300,” said Stohl.
After consulting paleofire records from each of the three regions, only one viable possibility remained: New Zealand, where charcoal records showed a major increase in fire activity beginning about the year 1300. This date also coincided with the estimated arrival, colonization, and subsequent burning of much of New Zealand’s forested areas by the Māori people.
This was a surprising conclusion, given New Zealand’s relatively small land area and the distance (nearly 4,500 miles), that smoke would have travelled to reach the ice core site on James Ross Island.
“Compared to natural burning in places like the Amazon, or Southern Africa, or Australia, you wouldn’t expect Māori burning in New Zealand to have a big impact, but it does over the Southern Ocean and the Antarctic Peninsula,” said Chellman, postdoctoral fellow at DRI. “Being able to use ice core records to show impacts on atmospheric chemistry that reached across the entire Southern Ocean, and being able to attribute that to the Māori arrival and settlement of New Zealand 700 years ago was really amazing.”
Black carbon deposition during the past 2000 years measured in ice cores from Dronning Maud Land in continental Antarctica and James Ross Island at the northern tip of the Antarctic Peninsula. Atmospheric modeling and local burning records indicate that the pronounced increase in deposition in the northern Antarctic Peninsula starting in the late 13th century was related to Māori settlement of New Zealand nearly 4000 miles away and their use of fire for land clearing and management. Inset shows locations of New Zealand and ice-core drilling sites in Antarctica.
Research impacts
The study findings are important for a number of reasons. First, the results have important implications for our understanding of Earth’s atmosphere and climate. Modern climate models rely on accurate information about past climate to make projections for the future, especially on emissions and concentrations of light-absorbing black carbon linked to Earth’s radiative balance. Although it is often assumed that human impacts during preindustrial times were negligible compared to background or natural burning, this study provides new evidence that emissions from human-related burning have impacted Earth’s atmosphere and possibly its climate far earlier, and at scales far larger, than previously imagined.
Second, fallout from biomass burning is rich in micronutrients such as iron. Phytoplankton growth in much of the Southern Ocean is nutrient-limited so the increased fallout from Māori burning probably resulted in centuries of enhanced phytoplankton growth in large areas of the Southern Hemisphere.
Third, the results refine what is known about the timing of the arrival of the Māori in New Zealand, one of the last habitable places on earth to be colonized by humans. Māori arrival dates based on radiocarbon dates vary from the 13th to 14th century, but the more precise dating made possible by the ice core records pinpoints the start of large scale burning by early Māori in New Zealand to 1297, with an uncertainty of 30 years.
“From this study and other previous work our team has done such as on 2,000-year old lead pollution in the Arctic from ancient Rome, it is clear that ice core records are very valuable for learning about past human impacts on the environment,” McConnell said. “Even the most remote parts of Earth were not necessarily pristine in preindustrial times.”
Measuring the chemistry in a longitudinal sample of an ice core on DRI’s unique ice core analytical system.
Additional information:
The full study, Hemispheric black carbon increase after 13th C Māori arrival in New Zealand, is available from Nature: https://www.nature.com/articles/s41586-021-03858-9
Study authors included Joseph R. McConnell (DRI), Nathan J. Chellman (DRI), Robert Mulvaney (British Antarctic Survey), Sabine Eckhardt (Norwegian Institute for Air Research), Andreas Stohl (University of Vienna), Gill Plunkett (Queen’s University Belfast), Sepp Kipfstuhl (Alfred Wegener Institut, Germany) , Johannes Freitag (Alfred Wegener Institut, Germany), Elisabeth Isaksson (Norwegian Polar Institute), Kelly E. Gleason (DRI/Portland State University), Sandra O. Brugger (DRI), David B. McWethy (Montana State University), Nerilie J. Abram (Australian National University), Pengfei Liu (Georgia Institute of Technology/Harvard University), and Alberto J. Aristarain (Instituto Antartico Argentino).
This study was made possible with funding from the National Science Foundation (0538416, 0968391, 1702830, 1832486, and 1925417), the DRI, and the Swiss National Science Foundation (P400P2_199285).
To learn more about DRI’s Ice Core Laboratory, please visit: https://www.dri.edu/labs/trace-chemistry-laboratory/.
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About DRI
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 who work alongside them, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge on topics ranging from humans’ impact on the environment to the environment’s impact on humans. DRI’s impactful science and inspiring solutions support Nevada’s diverse economy, provide science-based educational opportunities, and inform policymakers, business leaders, and community members. With campuses in Las Vegas and Reno, DRI serves as the non-profit research arm of the Nevada System of Higher Education. For more information, please visit www.dri.edu.
Sep 9, 2021 | News releases, Research findings
Study Shows A Recent Reversal in the Response of Western Greenland’s Ice Caps to Climate Change
Climate Change
Polar Research
Ice Cores
Above: A wide view of the Nuussuaq Peninsula in West Greenland. Project collaborators investigate an ice core extracted from this region for signs of change and response to past periods of warming.
Credit: Sarah Das © Woods Hole Oceanographic Institution
Research suggests some ice caps grew during past periods of warming
Although a warming climate is leading to rapid melting of the ice caps and glaciers along Greenland’s coastline, ice caps in this region sometimes grew during past periods of warming, according to new research published today in Nature Geoscience. The study team included Joseph McConnell, Nathan Chellman, and Monica Arienzo of DRI, who analyzed a 140 m ice core from an ice cap on Greenland’s Nuussuaq Peninsula at DRI’s Ice Core Laboratory in Reno, Nevada.
“The use of records from Greenland’s coastal ice caps in climate change research has been hampered by difficulties in creating chronologies for ice-core measurements,” said McConnell. “Here we used a novel approach based on synchronizing detailed measurements of heavy metals in an array of Greenland ice cores.”
“This allowed creation of a tightly constrained chronology in a coastal core for the first time, and it was this chronology that underpinned this climate study,” Chellman added.
The analysis was done using DRI’s unique continuous ice core analytical system, which was developed in McConnell’s lab and funded by grants from the National Science Foundation during the past 15 years.
The full news release from Woods Hole Oceanographic Institution is below.
Ice capped and snow-covered mountains of coastal west Greenland. (Apr. 2015)
Credit: Matthew Osman © Woods Hole Oceanographic Institution
News release reposted from Woods Hole Oceanographic Institution:
Woods Hole, Mass. (September 9, 2021) – Greenland may be best known for its enormous continental scale ice sheet that soars up to 3,000 meters above sea level, whose rapid melting is a leading contributor to global sea level rise. But surrounding this massive ice sheet, which covers 79% of the world’s largest island, is Greenland’s rugged coastline dotted with ice capped mountainous peaks. These peripheral glaciers and ice caps are now also undergoing severe melting due to anthropogenic (human-caused) warming. However, climate warming and the loss of these ice caps may not have always gone hand-in-hand.
New collaborative research from the Woods Hole Oceanographic Institution and five partner institutions (University of Arizona, University of Washington, Pennsylvania State University, Desert Research Institute and University of Bergen), published today in Nature Geoscience, reveals that during past periods glaciers and ice caps in coastal west Greenland experienced climate conditions much different than the interior of Greenland. Over the past 2,000 years, these ice caps endured periods of warming during which they grew larger rather than shrinking.
This novel study breaks down the climate history displayed in a core taken from an ice cap off Greenland’s western coast. According to the study’s researchers, while ice core drilling has been ongoing in Greenland since the mid-20th century, coastal ice core studies remain extremely limited, and these new findings are providing a new perspective on climate change compared to what scientists previously understood by using ice cores from the interior portions of the Greenland ice sheet alone.
“Glaciers and ice caps are unique high-resolution repositories of Earth’s climate history, and ice core analysis allows scientists to examine how environmental changes – like shifts in precipitation patterns and global warming – affect rates of snowfall, melting, and in turn influence ice cap growth and retreat,” said Sarah Das, Associate Scientist of Geology and Geophysics at WHOI. “Looking at differences in climate change recorded across several ice core records allows us to compare and contrast the climate history and ice response across different regions of the Arctic.” However, during the course of this study, it also became clear that many of these coastal ice caps are now melting so substantially that these incredible archives are in great peril of disappearing forever.
The research team on the ground of a coastal West Greenland ice cap, preparing to extract and examine ice cores.
Credit: Sarah Das © Woods Hole Oceanographic Institution
Due to the challenging nature of studying and accessing these ice caps, this team was the first to do such work, centering their study, which began in 2015, around a core collected from the Nuussuaq Peninsula in Greenland. This single core offers insight into how coastal climate conditions and ice cap changes covaried during the last 2,000 years, due to tracked changes in its chemical composition and the amount of snowfall archived year after year in the core. Through their analysis, investigators found that during periods of past warming, ice caps were growing rather than melting, contradicting what we see in the present day.
“Currently, we know Greenland’s ice caps are melting due to warming, further contributing to sea level rise. But, we have yet to explore how these ice caps have changed in the past due to changes in climate,” said Matthew Osman, postdoctoral research associate at the University of Arizona and a 2019 graduate of the MIT-WHOI Joint program. “The findings of this study were a surprise because we see that there is an ongoing shift in the fundamental response of these ice caps to climate: today, they’re disappearing, but in the past, within small degrees of warming, they actually tended to grow.”
According to Das and Osman, this phenomenon happens because of a “tug-of-war” between what causes an ice cap to grow (increased precipitation) or recede (increased melting) during periods of warming. Today, scientists observe melting rates that are outpacing the rate of annual snowfall atop ice caps. However, in past centuries these ice caps would expand due to increased levels of precipitation brought about by warmer temperatures. The difference between the past and present is the severity of modern anthropogenic warming.
The team gathered this data by drilling through an ice cap on top of one of the higher peaks of the Nuussuaq Peninsula. The entire core, about 140 meters in length, took about a week to retrieve. They then brought the meter-long pieces of core to the National Science Foundation Ice Core Facility in Denver, Colorado, and stored at -20 degrees Celsius. The core pieces were then analyzed by their layers for melt features and trace chemistry at the Desert Research Institute in Reno, Nevada. By looking at different properties of the core’s chemical content, such as parts per billion of lead and sulfur, investigators were able to accurately date the core by combining these measurements with a model of past glacier flow.
“These model estimates of ice cap flow, coupled with the actual ages that we have from this high precision chemistry, help us outline changes in ice cap growth over time. This method provides a new way of understanding past ice cap changes and how that is correlated with climate,” said Das. “Because we’re collecting a climate record from the coast, we’re able to document for the first time that there were these large shifts in temperature, snowfall and melt over the last 2,000 years, showing much more variability than is observed in records from the interior of Greenland,” Das added.
“Our findings should urge researchers to return to these remaining ice caps and collect new climate records while they still exist,” added Osman.
The research team on the ground of a coastal West Greenland ice cap, preparing to extract and examine ice cores.
Credit: Sarah Das © Woods Hole Oceanographic Institution
Additional collaborators and institutions:
- Benjamin Smith, University of Washington
- Luke Trusel, Pennsylvania State University
- Joseph McConnell, Desert Research Institute
- Nathan Chellman, Desert Research Institute
- Monica Arienzo, Desert Research Institute
- Harold Sodemann, University of Bergen and Bjerknes Centre for Climate Research
This research is funded by the National Science Foundation (NSF), with further support from the U.S. Department of Defense National Defense Science and Engineering Graduate Fellowship; and an Ocean Outlook Fellowship to the Bjerknes Centre for Climate Research; the National Infrastructure for High Performance Computing and Data Storage in Norway; Norwegian Research Council; and Air Greenland.
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About Woods Hole Oceanographic Institution
The Woods Hole Oceanographic Institution (WHOI) is a private, non-profit organization on Cape Cod, Massachusetts, dedicated to marine research, engineering, and higher education. Established in 1930, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate an understanding of the ocean’s role in the changing global environment. WHOI’s pioneering discoveries stem from an ideal combination of science and engineering—one that has made it one of the most trusted and technically advanced leaders in basic and applied ocean research and exploration anywhere. WHOI is known for its multidisciplinary approach, superior ship operations, and unparalleled deep-sea robotics capabilities. We play a leading role in ocean observation and operate the most extensive suite of data-gathering platforms in the world. Top scientists, engineers, and students collaborate on more than 800 concurrent projects worldwide—both above and below the waves—pushing the boundaries of knowledge and possibility. For more information, please visit www.whoi.edu
About DRI
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 who work alongside them, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge on topics ranging from humans’ impact on the environment to the environment’s impact on humans. DRI’s impactful science and inspiring solutions support Nevada’s diverse economy, provide science-based educational opportunities, and inform policymakers, business leaders, and community members. With campuses in Las Vegas and Reno, DRI serves as the non-profit research arm of the Nevada System of Higher Education. For more information, please visit www.dri.edu.
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
Mar 25, 2021 | Blog, Featured researchers
Meet Nathan Chellman, Ph.D.
Ice Cores
Climate Change
Environment
Meet DRI scientist Nathan Chellman and learn about his work in the Ice Core Laboratory in this interview with DRI’s Behind the Science Blog.
Nathan Chellman, Ph.D., is a postdoctoral fellow with the Division of Hydrologic Sciences at the Desert Research Institute (DRI) in Reno, Nev. He specializes in the collection, processing and analysis of ice cores — cylindrical samples of ice drilled from glaciers and ice sheets around the world. Nathan grew up in Reno, and holds a B.Sc. in Geology/Biology from Brown University, and M.S. and Ph.D. degrees in Hydrology from the University of Nevada, Reno. He first worked at DRI as a high school intern in 2008, then later returned to DRI during and after college to work with Joe McConnell in the Ice Core Lab. He received his helicopter private pilot license in 2014 and volunteered as an EMT while he was an undergraduate. In his free time, Nathan enjoys running, skiing, and backpacking in the Sierras and central Nevada.
Nathan Chellman, Ph.D., is a postdoctoral fellow with the Division of Hydrologic Sciences at the Desert Research Institute in Reno.
DRI: What do you do here at DRI?
Chellman: I work in the Ice Core Lab, where we do analyses and measurements on snow and ice from polar and alpine regions to learn about how the environment has changed over the past several centuries and millennia. I also do some work with tree rings and sediment cores from areas a little closer to home, like the Rocky Mountains, primarily looking at pollution and climate reconstructions.
DRI: What does an ice core look like, and how do you collect one?
Chellman: An ice core is a long, narrow cylinder of ice. To recover an ice core from an ice sheet or a glacier we use an ice core drill, which is a hollow tube with sharp cutters at one end and a big motor at the top. The motor spins the hollow tube, the cutters cut the ice away, and the ice core then ends up in the center of the hollow tube. You send the ice core drill down through the ice about 1 meter (3 feet) at a time, bring up the entire drill with an ice core inside, push the ice core out of the hollow drill section, send the drill back down the borehole, and then repeat that until you’re the whole way through the ice feature. For polar ice cores, we sometimes drill down hundreds of meters. So, we end up with hundreds or thousands of those meter-long sections back-to-back that represent a whole profile through the ice.
Above, left: Researchers process an ice core sample collected from a glacier in Greenland. Above, right: Closeup of an ice core drill.
Credit: Michaeol Sigl (left photo); Nathan Chellman/DRI (right photo).
DRI: What can you learn from all of these samples of ice? Can you tell us about one of your projects?
Chellman: One of my favorite projects right now is a study on some really old ice patches in Wyoming. These ice patches are about the size of a football field or smaller, so they are too small to be glaciers. They look just like little remnant snow patches that you might see in the Sierra Nevada if you go out hiking in the late summer. However, they’re not snowdrifts, they’re actual ice – and some of these ice patches are turning out to be thousands and thousands of years old.
I was invited to join the project by a group of archaeologists and climate scientists who were interested in looking at how old the ice patches were, and studying the organic debris inside of them and the artifacts that were melting out around the edges. They didn’t know what to do with the ice itself, but since we specialize in measuring ice chemistry, I volunteered to go to their field site when they were drilling through a shallow ice patch and bring some ice back to DRI. Those samples ended up being a very nice record of ice chemistry. The ice patch turned out to be 10,000 years old at the bottom, with about 30 organic layers cutting through the ice.
Normally in an ice core project, if you have dirt and organic layers in your ice core you’ve done something terribly wrong. In this case, the dirt was the key to unlocking how old the ice patch was, since the age of the organic material can be accurately dated. It turned out that the chemistry of the ice was really interesting as well, and preserved some climate information going back over ten thousand years. You can see distinct warm and cold periods that paralleled lake sediment records from nearby, and also some anthropological records of population. So, that suggested that people living in the area were affected by the general climate conditions as indicated by the ice patch chemistry.
Above, left: Nathan Chellman carries ice coring equipment to an alpine ice patch, where he and his colleagues are using ice core records from an isolated ice patch to learn about ancient climate in the region. Above, right: Chellman holds an ice core sample collected from an alpine ice patch.
Credit: Monica Arienzo/DRI.
DRI: Have you ever been part of a polar drilling operation?
Chellman: Yes, in 2013 I was in northeastern Greenland. That year we recovered a 212-meter ice core, which went back about 1,700 years. It took about two weeks working normal 8- or 10-hour days – but as you drill deeper and deeper into the ice, it takes longer and longer for the drill to go up and down the borehole. On the first day you can go about 20 meters in a day, and the next day you can go a little less, and by the end you’re only drilling 6 to 10 meters per day because it takes so long for the drill to go up and down the hole.
The first day was terrifying. The plane landed out in the middle of the ice sheet, hundreds of miles from any other camps or bases. The pilot dropped us and our gear out in the snow, and then took off and left. Help was a few days away at best, so we had to just get working and get camp set up before everything blew away, because it’s always windy there. There were no buildings, no infrastructure, just us and our camping gear. We had personal sleeping tents (we each used two sleeping bags!), a kitchen tent, and a science tent, as well as plenty of food, Coleman stoves for cooking, and the ice core drill.
DRI: What were the working conditions like in Greenland?
Chellman: The strangest part about working in Greenland during the summer is that it’s never night. The sun never completely goes down, even at night. The sun goes low on the horizon and it gets colder, but it’s never actually dark. It’s a little disorienting at first. You have to sleep with eye covers or pull your hat down over your eyes so you can pretend like you’re in a little bit of darkness.
It was also really cold. Between -25 and -35C (-13 to -31F) at night, and anywhere between -5 and -15C (23F to 5F) during the day. When it’s that cold, it’s really interesting because you have to consider that everything is going to be frozen. Your toothpaste is going to be frozen, if you leave your water in a mug it’s going to be frozen. It requires some adaptations from a lifestyle perspective to make sure what you need isn’t going to be a total block of ice.
In 2013, Chellman and his colleagues traveled to northeastern Greenland to collect a 212-meter ice core that went back 1,700 years. Their field camp is pictured here.
Credit: Nathan Chellman/DRI.
DRI: Do you have any plans to return?
Chellman: We were supposed to go back last year to that same place in Greenland and get an ice core that was twice as long, but that was postponed. We’re rescheduling for this spring, but everything is still very much up in the air. If we go, we’ll be gathering data for a study that is trying to understand pollution from ancient societies. For example, we will be looking to see if we can detect Bronze Age pollution from 2,000-3,000 years ago in the ice. The pollution would have been caused by mining and smelting of metals.
DRI: It sounds like you have a very exciting job. What do you like best about what you do?
Chellman: One of my favorite things is actually being in the lab and making the measurements, and taking all the time to make sure everything is running right, and that the analytical system and all the instruments are making high-quality measurements. When you’re analyzing ice cores, you have to be consistent day to day and week to week, since sometimes it can take a month or two to analyze all the samples from an ice core. But it’s really fun to get in the groove in the lab, run long days, and generate really consistent, nice datasets. There’s a lot of troubleshooting involved, but once the system is running smoothly, it’s really amazing to be able to generate unique, one-of-a-kind data that can be trusted to inform really big picture questions.
Additional Information:
For more information on Nathan Chellman and his research, please visit: https://www.dri.edu/directory/nathan-chellman/
For more information on the DRI Ice Core Laboratory, please visit: https://www.dri.edu/labs/trace-chemistry-laboratory/
DRI scientist Nathan Chellman.
Credit: Nathan Chellman/DRI.
Jun 22, 2020 | News releases, Research findings
Reno, Nev. (June 22, 2020) – An international team of scientists and historians has found evidence connecting an unexplained period of extreme cold in ancient Rome with an unlikely source: a massive eruption of Alaska’s Okmok volcano, located on the opposite side of the Earth.
Around the time of Julius Caesar’s death in 44 BCE, written sources describe a period of unusually cold climate, crop failures, famine, disease, and unrest in the Mediterranean Region – impacts that ultimately contributed to the downfall of the Roman Republic and Ptolemaic Kingdom of Egypt. Historians have long suspected a volcano to be the cause, but have been unable to pinpoint where or when such an eruption had occurred, or how severe it was.
In a new study published this week in Proceedings of the National Academy of Sciences (PNAS), a research team led by Joe McConnell, Ph.D. of the Desert Research Institute in Reno, Nev. uses an analysis of tephra (volcanic ash) found in Arctic ice cores to link the period of unexplained extreme climate in the Mediterranean with the caldera-forming eruption of Alaska’s Okmok volcano in 43 BCE.
“To find evidence that a volcano on the other side of the earth erupted and effectively contributed to the demise of the Romans and the Egyptians and the rise of the Roman Empire is fascinating,” McConnell said. “It certainly shows how interconnected the world was even 2,000 years ago.”
Alaska’s Umnak Island in the Aleutians showing the huge, 10-km wide caldera (upper right) largely created by the 43 BCE Okmok II eruption at the dawn of the Roman Empire. Landsat-8 Operational Land Imager image from May 3, 2014. Credit: U.S. Geological Survey.
The discovery was initially made last year in DRI’s Ice Core Laboratory, when McConnell and Swiss researcher Michael Sigl, Ph.D. from the Oeschger Centre for Climate Change Research at the University of Bern happened upon an unusually well-preserved layer of tephra in an ice core sample and decided to investigate.
New measurements were made on ice cores from Greenland and Russia, some of which were drilled in the 1990s and archived in the U.S., Denmark, and Germany. Using these and earlier measurements, they were able to clearly delineate two distinct eruptions – a powerful but short-lived, relatively localized event in early 45 BCE, and a much larger and more widespread event in early 43 BCE with volcanic fallout that lasted more than two years in all the ice core records.
The researchers then conducted a geochemical analysis of the tephra samples from the second eruption found in the ice, matching the tiny shards with those of the Okmok II eruption in Alaska – one of the largest eruptions of the past 2,500 years.
“The tephra match doesn’t get any better,” said tephra specialist Gill Plunkett, Ph.D. from Queen’s University Belfast. “We compared the chemical fingerprint of the tephra found in the ice with tephra from volcanoes thought to have erupted about that time and it was very clear that the source of the 43 BCE fallout in the ice was the Okmok II eruption.”
Detailed records of past explosive volcanic eruptions are archived in the Greenland ice sheet and accessed through deep-drilling operations. Credit: Dorthe Dahl-Jensen.
Working with colleagues from the U.K., Switzerland, Ireland, Germany, Denmark, Alaska, and Yale University in Connecticut, the team of historians and scientists gathered supporting evidence from around the globe, including tree-ring-based climate records from Scandinavia, Austria and California’s White Mountains, and climate records from a speleothem (cave formations) from Shihua Cave in northeast China. They then used Earth system modeling to develop a more complete understanding of the timing and magnitude of volcanism during this period and its effects on climate and history.
According to their findings, the two years following the Okmok II eruption were some of the coldest in the Northern Hemisphere in the past 2,500 years, and the decade that followed was the fourth coldest. Climate models suggest that seasonally averaged temperatures may have been as much as 7oC (13oF) below normal during the summer and autumn that followed the 43 BCE eruption of Okmok, with summer precipitation of 50 to 120 percent above normal throughout Southern Europe, and autumn precipitation reaching as high as 400 percent of normal.
“In the Mediterranean region, these wet and extremely cold conditions during the agriculturally important spring through autumn seasons probably reduced crop yields and compounded supply problems during the ongoing political upheavals of the period,” said classical archaeologist Andrew Wilson, D.Phil. of the University of Oxford. “These findings lend credibility to reports of cold, famine, food shortage and disease described by ancient sources.”
“Particularly striking was the severity of the Nile flood failure at the time of the Okmok eruption, and the famine and disease that was reported in Egyptian sources,” added Yale University historian Joe Manning, Ph.D. “The climate effects were a severe shock to an already stressed society at a pivotal moment in history.”
Timeline showing European summer temperatures and volcanic sulphur and ash levels in relation to the Okmok II Eruption and significant historic events of the Roman Republic and Ptolemaic Kingdom from 59 to 20 BCE.
Volcanic activity also helps to explain certain unusual atmospheric phenomena that were described by ancient Mediterranean sources around the time of Caesar’s assassination and interpreted as signs or omens – things like solar halos, the sun darkening in the sky, or three suns appearing in the sky (a phenomenon now known as a parahelia, or ‘sun dog’). However, many of these observations took place prior to the eruption of Okmok II in 43 BCE, and are likely related to a smaller eruption of Mt. Etna in 44 BCE.
Although the study authors acknowledge that many different factors contributed to the fall of the Roman Republic and Ptolemaic Kingdom, they believe that the climate effects of the Okmok II eruption played an undeniably large role – and that their discovery helps to fill a knowledge gap about this period of history that has long puzzled archaeologists and ancient historians.
“People have been speculating about this for many years, so it’s exciting to be able to provide some answers,” McConnell said.
Additional information
This project received support from the National Science Foundation, the Sir Nicholas Shackleton Visiting Fellowship, Clare Hall, Cambridge and the John Fell Oxford University Press Research Fund. Additional authors from DRI included Nathan Chellman, Ph.D.
To view the full text of the article “Extreme climate after massive eruption of Alaska’s Okmok volcano in 43 BCE and effects on the late Roman Republic and Ptolemaic Kingdom” in PNAS, please visit: [add link]
For more information on lead author Joe McConnell, Ph.D., and his research, please visit: https://www.dri.edu/directory/joe-mcconnell/
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About the Desert Research Institute
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 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, visit www.dri.edu.
Jul 8, 2019 | News releases, Research findings
Photo: Dr. Joe McConnell and graduate student Nathan Chellman work in the ice lab at the Desert Research Institute, in Reno, Nev., on Wednesday, May 15, 2019. Photo by Cathleen Allison/Nevada Momentum.
RENO, Nev. (July 8, 2019) – How did events like the Black Death plague impact the economy of Medieval Europe? Particles of lead trapped deep in Arctic ice can tell us.
Commercial and industrial processes have emitted lead into the atmosphere for thousands of years, from the mining and smelting of silver ores to make currency for ancient Rome to the burning of fossil fuels today. This lead pollution travels on wind currents through the atmosphere, eventually settling on places like the ice sheet in Greenland and other parts of the Arctic.
Because of lead’s connection to precious metals like silver and the fact that natural lead levels in the environment are very low, scientists have found that lead deposits in layers of Arctic ice are a sensitive indicator of overall economic activity throughout history.
In a new study published in the Proceedings of the National Academy of Sciences, researchers from the Desert Research Institute (DRI), the University of Oxford, NILU – Norwegian Institute for Air Research, the University of Copenhagen, the University of Rochester, the Alfred Wegener Institute for Polar and Marine Research used thirteen Arctic ice cores from Greenland and the Russian Arctic to measure, date, and analyze lead emissions captured in the ice from 500 to 2010 CE, a period of time that extended from the Middle Ages through the Modern Period to the present.
This work builds on a study published by some of the same researchers in 2018, which showed how lead pollution in a single ice core from Greenland tracked the ups and downs of the European economy between 1100 BCE and 800 CE, a period which included the Greek and Roman empires.
“We have extended our earlier record through the Middle Ages and Modern Period to the present,” explained Joe McConnell, Ph.D., lead author on the study and Director of DRI’s Ultra-Trace Ice Core Chemistry Laboratory in Reno, Nevada. “Using an array of thirteen ice cores instead of just one, this new study shows that prior to the Industrial Revolution, lead pollution was pervasive and surprisingly similar across a large swath of the Arctic and undoubtedly the result of European emissions. The ice-core array provides with amazing detail a continuous record of European – and later North American – industrial emissions during the past 1500 years.”
“Developing and interpreting such an extensive array of Arctic ice-core records would have been impossible without international collaboration,” McConnell added.
The research team found that increases in lead concentration in the ice cores track closely with periods of expansion in Europe, the advent of new technologies, and economic prosperity. Decreases in lead, on the other hand, paralleled climate disruptions, wars, plagues, and famines.
“Sustained increases in lead pollution during the Early and High Middle Ages (about 800 to 1300 CE), for example, indicate widespread economic growth, particularly in central Europe as new mining areas were discovered in places like the German Harz and Erzgebirge Mountains, “McConnell noted. “Lead pollution in the ice core records declined during the Late Middle Ages and Early Modern Period (about 1300 to 1680 Ce) when plague devastated those regions, however, indicating that economic activity stalled.”
Even with ups and downs over time due to events such as plagues, the study shows that increases in lead pollution in the Arctic during the past 1500 years have been exponential.
“We found an overall 250 to 300-fold increase in Arctic lead pollution from the start of the Middle Ages in 500 CE to 1970s,” explained Nathan Chellman, a doctoral student at DRI and coauthor on the study. “Since the passage of pollution abatement policies, including the 1970 Clean Air Act in the United States, lead pollution in Arctic ice has declined more than 80 percent.”
“Still, lead levels are about 60 times higher today than they were at the beginning of the Middle Ages,” Chellman added.
This study included an array of ice cores and the research team used state-of-the-art atmospheric modeling to determine the relative sensitivity of different ice-core sites in the Arctic to lead emissions.
“Modeling shows that the core from the Russian Arctic is more sensitive to European emissions, particularly from eastern parts of Europe, than cores from Greenland,” explained Andreas Stohl, Ph.D., an atmospheric scientist at NILU and coauthor on the study. “This is why we found consistently higher levels of lead pollution in the Russian Arctic core and more rapid increases during the Early and High Middle Ages as mining operations shifted north and east from the Iberian Peninsula to Great Britain and Germany.”
Lead pollution found in 13 ice cores from three different regions of the Arctic (North Greenland, South Greenland, and the Russian Arctic) from 200 BCE to 2010 CE. Increases in lead deposition coincided with times of economic prosperity, such as the Industrial Revolution in the mid-19th century. Dramatic declines in lead pollution followed crises such as the Black Death Plague Pandemic starting about 1347 CE, as well as pollution abatement policies such as the 1970 U.S. Clean Air Act.
The combination of expertise on this study is unique, continuing collaboration between researchers in fields as different as ice-core chemistry and economic history. These results, the team argues, are a testament to the benefits of interdisciplinary collaboration.
“What we’re finding is interesting not just to environmental scientists who want to understand how human activity has altered the environment,” said Andrew Wilson, Ph.D., Professor of the Archaeology of the Roman Empire at Oxford and co-author on the study. “These ice-core records also are helping historians to understand and quantify the ways that societies and their economies have responded to external forces such as climate disruptions, plagues, or political unrest.”
Collection, analysis, and interpretation of the ice cores used in this study were supported by the U.S. National Science Foundation, NASA, the John Fell Oxford University Press Research Fund and All Souls College, Oxford, the German Ministry of Education and Research, the German Research Foundation, and the Desert Research Institute.
Locations of the 13 Arctic ice-core drilling sites, as well as ancient and medieval lead/silver mines throughout Europe. Atmospheric modeling shows the impact of emissions from different regions on pollution recorded in the Arctic ice cores. The Russian Arctic, for example, is relatively more sensitive to emissions from mines in eastern Europe, while North Greenland is relatively more sensitive to emissions from western Europe.
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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 policymakers, 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. Learn more at www.dri.edu, and connect with us on social media on Facebook, Instagram, and Twitter.
Media Contact:
Justin Broglio
Communications Manager, Desert Research Institute
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775-673-7610
@DRIscience
May 9, 2019 | News releases, Research findings
Researchers drill ice cores from a field camp on Mont Blanc in the French Alps. Credit: B. Jourdain, L’Institut des Géosciences de l’Environnement.
RENO, Nev. (May 8, 2019) – Last spring, an international team of researchers led by Joe McConnell, PhD, Director of the Ultra Trace Ice Core Chemistry Laboratory at DRI’s campus in Reno, Nevada, traced significant atmospheric lead pollution from Roman-era mining and smelting of lead-silver ores in an ice core record from Greenland, providing new insights about the Roman economy.
Now working with colleagues at the Institute of Geosciences and the Environment in Grenoble, France, some members of the same research team have published findings that show a related record of pollution in an ice core from the Col du Dôme area of Mont Blanc in the French Alps.
Published in Geophysical Research Letters, the new study reveals significant atmospheric pollution from lead and antimony, another toxic heavy metal. This study is the first to document an ice core record of antimony, showing that Roman-era mining and smelting activities had implications beyond lead contamination.
Lead (black) and antimony (red) concentrations in ice from the Col du Dôme (CDD). On the bottom scale, age is indicated in years. Phases of increasing lead emissions were accompanied by a simultaneous rise in the presence of antimony – another toxic metal – in the alpine ice. The increases and decreases in heavy metal concentration in the ice correspond with boom times and crises in Roman-era economic history.
“This is the first study of antiquity-era pollution using Alpine ice,” explained lead author Susanne Preunkert, PhD, of the CNRS Institute of Geosciences and the Environment. “Our record from the Alps provides insight into the impact of ancient emissions on the present-day environment in Europe, as well as a comparison with more recent pollution linked to the use of leaded gasoline in the twentieth century.”
Compared to the lead pollution record obtained from a Greenland ice core in the previous study, which reflects heavy metal emissions from across Europe, the Mont Blanc ice core reflects influences from more local pollution sources.
“This study continues an international collaboration between ice core experts, historians, and atmospheric scientists,” said McConnell. “Cross-disciplinary research like this allows us to interpret the ice record in more detail, leading to a better understanding of the impacts of past human activities on the natural environment while also providing new, more quantitative information on those human activities.”
This research received support from the CNRS, ADEME, and the European Alpclim and Carbosol projects, as well as the Desert Research Institute.
The full study, titled “Lead and Antimony in Basal Ice From Col du Dome (French Alps) Dated With Radiocarbon: A Record of Pollution During Antiquity,” is available here.
François Maginiot of CNRS contributed to this release.
May 7, 2019 | News releases, Research findings
Researchers use a drill to extract one of the Greenland ice core samples that became the basis for this research. Credit: Joe McConnell/DRI.
RENO, Nev. (May 7, 2019) – This week, new research outlining the steady decline of phytoplankton productivity in the North Atlantic since the Industrial Revolution was published in the journal Nature. The study, titled “Industrial-era decline in subarctic Atlantic productivity,” 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 uses measurements from twelve Greenland ice cores to trace the amount of methanesulfonic acid (MSA)—a byproduct of the emissions from large phytoplankton blooms—in the atmosphere. Since the mid-19th century, the concentration of MSA in ice core records has declined by about 10 percent, which translates to a 10 percent loss of phytoplankton. This loss coincides with steadily rising ocean surface temperatures over the same time period, which suggests that populations may decline further as temperatures continue to rise.
A full press release about these findings, originally published by MIT News, is available below.
North Atlantic Ocean productivity has dropped 10 percent during Industrial era
Phytoplankton decline coincides with warming temperatures over the last 150 years.
Jennifer Chu | MIT News Office
May 6, 2019
Virtually all marine life depends on the productivity of phytoplankton — microscopic organisms that work tirelessly at the ocean’s surface to absorb the carbon dioxide that gets dissolved into the upper ocean from the atmosphere.
Through photosynthesis, these microbes break down carbon dioxide into oxygen, some of which ultimately gets released back to the atmosphere, and organic carbon, which they store until they themselves are consumed. This plankton-derived carbon fuels the rest of the marine food web, from the tiniest shrimp to giant sea turtles and humpback whales.
Now, scientists at MIT, Woods Hole Oceanographic Institution (WHOI), and elsewhere have found evidence that phytoplankton’s productivity is declining steadily in the North Atlantic, one of the world’s most productive marine basins.
In a paper appearing today in Nature, the researchers report that phytoplankton’s productivity in this important region has gone down around 10 percent since the mid-19th century and the start of the Industrial era. This decline coincides with steadily rising surface temperatures over the same period of time.
Matthew Osman, the paper’s lead author and a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences and the MIT/WHOI Joint Program in Oceanography, says there are indications that phytoplankton’s productivity may decline further as temperatures continue to rise as a result of human-induced climate change.
“It’s a significant enough decline that we should be concerned,” Osman says. “The amount of productivity in the oceans roughly scales with how much phytoplankton you have. So this translates to 10 percent of the marine food base in this region that’s been lost over the industrial era. If we have a growing population but a decreasing food base, at some point we’re likely going to feel the effects of that decline.”
Drilling through “pancakes” of ice
Osman and his colleagues looked for trends in phytoplankton’s productivity using the molecular compound methanesulfonic acid, or MSA. When phytoplankton expand into large blooms, certain microbes emit dimethylsulfide, or DMS, an aerosol that is lofted into the atmosphere and eventually breaks down as either sulfate aerosol, or MSA, which is then deposited on sea or land surfaces by winds.
“Unlike sulfate, which can have many sources in the atmosphere, it was recognized about 30 years ago that MSA had a very unique aspect to it, which is that it’s only derived from DMS, which in turn is only derived from these phytoplankton blooms,” Osman says. “So any MSA you measure, you can be confident has only one unique source — phytoplankton.”
In the North Atlantic, phytoplankton likely produced MSA that was deposited to the north, including across Greenland. The researchers measured MSA in Greenland ice cores — in this case using 100- to 200-meter-long columns of snow and ice that represent layers of past snowfall events preserved over hundreds of years.
“They’re basically sedimentary layers of ice that have been stacked on top of each other over centuries, like pancakes,” Osman says.
The team analyzed 12 ice cores in all, each collected from a different location on the Greenland ice sheet by various groups from the 1980s to the present. Osman and his advisor Sarah Das, an associate scientist at WHOI and co-author on the paper, collected one of the cores during an expedition in April 2015.
“The conditions can be really harsh,” Osman says. “It’s minus 30 degrees Celsius, windy, and there are often whiteout conditions in a snowstorm, where it’s difficult to differentiate the sky from the ice sheet itself.”
The team was nevertheless able to extract, meter by meter, a 100-meter-long core, using a giant drill that was delivered to the team’s location via a small ski-equipped airplane. They immediately archived each ice core segment in a heavily insulated cold storage box, then flew the boxes on “cold deck flights” — aircraft with ambient conditions of around minus 20 degrees Celsius. Once the planes touched down, freezer trucks transported the ice cores to the scientists’ ice core laboratories.
“The whole process of how one safely transports a 100-meter section of ice from Greenland, kept at minus-20-degree conditions, back to the United States is a massive undertaking,” Osman says.
Cascading effects
The team incorporated the expertise of researchers at various labs around the world in analyzing each of the 12 ice cores for MSA. Across all 12 records, they observed a conspicuous decline in MSA concentrations, beginning in the mid-19th century, around the start of the Industrial era when the widescale production of greenhouse gases began. This decline in MSA is directly related to a decline in phytoplankton productivity in the North Atlantic.
“This is the first time we’ve collectively used these ice core MSA records from all across Greenland, and they show this coherent signal. We see a long-term decline that originates around the same time as when we started perturbing the climate system with industrial-scale greenhouse-gas emissions,” Osman says. “The North Atlantic is such a productive area, and there’s a huge multinational fisheries economy related to this productivity. Any changes at the base of this food chain will have cascading effects that we’ll ultimately feel at our dinner tables.”
The multicentury decline in phytoplankton productivity appears to coincide not only with concurrent long-term warming temperatures; it also shows synchronous variations on decadal time-scales with the large-scale ocean circulation pattern known as the Atlantic Meridional Overturning Circulation, or AMOC. This circulation pattern typically acts to mix layers of the deep ocean with the surface, allowing the exchange of much-needed nutrients on which phytoplankton feed.
In recent years, scientists have found evidence that AMOC is weakening, a process that is still not well-understood but may be due in part to warming temperatures increasing the melting of Greenland’s ice. This ice melt has added an influx of less-dense freshwater to the North Atlantic, which acts to stratify, or separate its layers, much like oil and water, preventing nutrients in the deep from upwelling to the surface. This warming-induced weakening of the ocean circulation could be what is driving phytoplankton’s decline. As the atmosphere warms the upper ocean in general, this could also further the ocean’s stratification, worsening phytoplankton’s productivity.
“It’s a one-two punch,” Osman says. “It’s not good news, but the upshot to this is that we can no longer claim ignorance. We have evidence that this is happening, and that’s the first step you inherently have to take toward fixing the problem, however we do that.”
This research was supported in part by the National Science Foundation (NSF), the National Aeronautics and Space Administration (NASA), as well as graduate fellowship support from the US Department of Defense Office of Naval Research.
Reprinted with permission of MIT News.
May 2, 2019 | News releases, Research findings
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.
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.
Mar 1, 2019 | Announcements, News releases
Reno, Nev. (March 1, 2019): This week, the Nevada System of Higher Education (NSHE) Board of Regents awarded Monica Arienzo, Ph.D. of the Desert Research Institute (DRI) in Reno with its annual Rising Researcher Award. The honor is given annually to one NSHE faculty member from DRI, UNR, and UNLV.
Arienzo is an assistant research professor of hydrology with DRI’s Division of Hydrologic Sciences. She was recognized for her early-career accomplishments using geochemical tools to understand climatic changes of the past and human impacts to the environment, and for her commitment to sharing her research with the scientific community, the greater Nevada community, and with students.
As a member of DRI’s Ice Core Laboratory, Arienzo and her collaborators have published climate records extending 100,000 years into the past. Her work also has focused on emissions from anthropogenic processes since the industrial revolution. Using ice cores from Greenland, Antarctica, and the European Alps, this research demonstrated the geographic extent of anthropogenic emissions, variations in emissions through time, and sources of these emissions. Locally, her work includes a project partnering with a Nevada non-profit organization to assess the impact of pollutants to the Tahoe Basin snow and water resources.
“I am honored to receive this award,” Arienzo said. “I look forward to continuing this important work with our team at DRI to understand interactions between the environment, climate, and human activities.”
With her collaborators, Dr. Arienzo is at the forefront in development of new geochemical methods including extraction of small (<1µL) water samples from stalagmites, analysis of formation temperatures for carbonates, and novel dating techniques for ice cores. She is currently collaborating with researchers at eight different institutions in four countries on a variety of interdisciplinary research projects.
Since joining DRI, Dr. Arienzo has been the lead author on four and co-author on ten peer-reviewed manuscripts published in high-impact journals including Proceedings of the National Academy of Sciences, Environmental Science and Technology, and Earth and Planetary Science Letters.
Arienzo holds a B.A. in geology from Franklin and Marshall College and a Ph.D. in marine geology and geophysics from the University of Miami’s Rosenstiel School of Marine and Atmospheric Science. She joined DRI in 2014 as a Postdoctoral Fellow under the mentorship of Dr. Joe McConnell, and was promoted to Assistant Research Professor in 2016.
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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.
Jan 17, 2019 | Awards and Honors, Blog
Reno, Nev. (Thurs. January 17th) – For the second time, research out of the Ultra-trace Ice Core Chemistry Laboratory at the Desert Research Institute (DRI) in Reno, Nevada, has been named one of the year’s biggest scientific discoveries by Discover magazine.
The research, originally published in the Proceedings of the National Academies of Science last May, used ice samples from the North Greenland Ice Core Project (NGRIP) to measure, date, and analyze European lead emissions that were captured in Greenland ice between 1100 BC and AD 800. Their results provide new insights for historians about how European civilizations and their economies fared over time.
“Our record of sub-annually resolved, accurately dated measurements in the ice core starts in 1100 BC during the late Iron Age and extends through antiquity and late antiquity to the early Middle Ages in Europe, a period that included the rise and fall of the Greek and Roman civilizations,” said the study’s lead author Joe McConnell, Ph.D., Research Professor of Hydrology at DRI and Director of the Ice Core Lab. “We found that lead pollution in Greenland very closely tracked known plagues, wars, social unrest and imperial expansions during European antiquity.”
The research team on the project included scientists, archaeologists, and economists from the Desert Research Institute (DRI), the University of Oxford, NILU – Norwegian Institute for Air Research and the University of Copenhagen.
This is the second time research out of the DRI Ice Core Lab has been recognized in the Discover magazine round up of the year’s top science stories. In the January 2008 issue, findings on rising black carbon levels in Greenland ice cores during the industrial revolution made the magazine’s 2007 top 100 list.
“Selection of these findings as among the world’s top science stories of 2018 is very exciting for the members of our research group and our international collaborators. It is especially rewarding for me in that a largely ice core based study was selected as among the top stories in archaeology rather than in earth or environmental sciences. This all demonstrates the vast potential of highly interdisciplinary research teams working together.”
Other DRI researchers who worked on this study are Monica Arienzo, Ph.D., assistant research professor, and graduate student researcher Nathan Chellman.
Dec 5, 2018 | News releases, Research findings
Reno, Nev. (Dec. 5, 2018): The melting of the Greenland ice sheet has increased rapidly in response to Arctic warming, and is likely to continue to do so into the future, according to new research from an international team of scientists including Joe McConnell, Ph.D., of the Desert Research Institute in Reno. Among other findings, their research shows a 250 to 575 percent increase in melt intensity over the last 20 years.
This study team utilized ice cores to reconstruct past melting rates from the present day back to the 1600s, producing the first continuous, multi-century record of surface melt intensity and runoff from the Greenland ice sheet. Previous studies have utilized satellite observations, which only go back to 1978.
McConnell, who is a research professor of hydrology and head of the Ultra-Trace Ice Core Analytical Laboratory at DRI, first became involved in the study in 2003 when his research group drilled and analyzed the contents of a 150-meter (492-foot) ice core from west-central Greenland. This ice core, known as “D5”, was then used by Sarah Das, Ph.D. from Woods Hole Oceanographic Institution (WHOI) to develop the record of surface melting rates used in this study.
In a subsequent 2016 collaboration with WHOI researchers, McConnell’s group also used DRI’s unique continuous ice-core analytical system to analyze a 115-meter (377-foot) ice core known as “NU”, which was collected in 2015 by the study’s lead author Luke Trusel and colleagues. The detailed DRI measurements of more than 20 elements and chemical species in both the D5 and NU ice cores enabled precise dating of the records that underpin the new findings.
Recovering an ice core from west Greenland. Credit: Sarah Has/Woods Hole Oceanographic Institution
The study, titled “Nonlinear Rise in Greenland Runoff in Response to Post-industrial Arctic Warming”, was published in the journal Nature in on December 5, 2018: https://doi.org/10.1038/s41586-018-0752-4. A detailed press release from Woods Hole Oceanographic Institution is below.
Greenland Ice Sheet Melt ‘Off the Charts’ Compared with Past Four Centuries
Surface melting across Greenland’s mile-thick ice sheet began increasing in the mid-19th century and then ramped up dramatically during the 20th and early 21st centuries, showing no signs of abating, according to new research published Dec. 5, 2018, in the journal Nature. The study provides new evidence of the impacts of climate change on Arctic melting and global sea level rise.
“Melting of the Greenland Ice Sheet has gone into overdrive. As a result, Greenland melt is adding to sea level more than any time during the last three and a half centuries, if not thousands of years,” said Luke Trusel, a glaciologist at Rowan University’s School of Earth & Environment and former post-doctoral scholar at Woods Hole Oceanographic Institution, and lead author of the study. “And increasing melt began around the same time as we started altering the atmosphere in the mid-1800s.”
“From a historical perspective, today’s melt rates are off the charts, and this study provides the evidence to prove this,” said Sarah Das, a glaciologist at Woods Hole Oceanographic Institution (WHOI) and co-author of the study. “We found a fifty percent increase in total ice sheet meltwater runoff versus the start of the industrial era, and a thirty percent increase since the 20th century alone.”
Meltwater lakes on the Greenland ice sheet. Credit: Sarah Das/Woods Hole Oceanographic Institution.
Ice loss from Greenland is one of the key drivers of global sea level rise. Icebergs calving into the ocean from the edge of glaciers represent one component of water re-entering the ocean and raising sea levels. But more than half of the ice-sheet water entering the ocean comes from runoff from melted snow and glacial ice atop the ice sheet. The study suggests that if Greenland ice sheet melting continues at “unprecedented rates”—which the researchers attribute to warmer summers—it could accelerate the already fast pace of sea level rise.
“Rather than increasing steadily as climate warms, Greenland will melt increasingly more and more for every degree of warming. The melting and sea level rise we’ve observed already will be dwarfed by what may be expected in the future as climate continues to warm,” said Trusel.
To determine how intensely Greenland ice has melted in past centuries, the research team used a drill the size of a traffic light pole to extract ice cores from the ice sheet itself and an adjacent coastal ice cap, at sites more than 6,000 feet above sea level. The scientists drilled at these elevations to ensure the cores would contain records of past melt intensity, allowing them to extend their records back into the 17th century.
During warm summer days in Greenland, melting occurs across much of the ice sheet surface. At lower elevations, where melting is the most intense, meltwater runs off the ice sheet and contributes to sea level rise, but no record of the melt remains. At higher elevations, however, the summer meltwater quickly refreezes from contact with the below-freezing snowpack sitting underneath. This prevents it from escaping the ice sheet in the form of runoff. Instead, it forms distinct icy bands that stack up in layers of densely packed ice over time.
The core samples were brought back to ice core labs at the U.S. National Science Foundation Ice Core Facility in Denver, Colo., WHOI in Woods Hole, Mass., Wheaton College in Norton, Mass., and the Desert Research Institute in Reno, Nev. where the scientists measured physical and chemical properties along the cores to determine the thickness and age of the melt layers. Dark bands running horizontally across the cores, like ticks on a ruler, enabled the scientists to visually chronicle the strength of melting at the surface from year to year. Thicker melt layers represented years of higher melting, while thinner sections indicated years with less melting.
Iceberg in Disko Bay, west Greenland. Credit Luke Trusel/Rowan University.
Combining results from multiple ice cores with observations of melting from satellites and sophisticated climate models, the scientists were able to show that the thickness of the annual melt layers they observed clearly tracked not only how much melting was occurring at the coring sites, but also much more broadly across Greenland. This breakthrough allowed the team to reconstruct meltwater runoff at the lower-elevation edges of the ice sheet—the areas that contribute to sea level rise.
Ice core records provide critical historical context because satellite measurements—which scientists rely on today to understand melting rates in response to changing climate—have only been around since the late 1970s, said Matt Osman, a graduate student in the MIT-WHOI Joint Program and co-author of the study.
“We have had a sense that there’s been a great deal of melting in recent decades, but we previously had no basis for comparison with melt rates going further back in time,” he said. “By sampling ice, we were able to extend the satellite data by a factor of 10 and get a clearer picture of just how extremely unusual melting has been in recent decades compared to the past.”
Trusel said the new research provides evidence that the rapid melting observed in recent decades is highly unusual when put into a historical context.
“To be able to answer what might happen to Greenland next, we need to understand how Greenland has already responded to climate change,” he said. “What our ice cores show is that Greenland is now at a state where it’s much more sensitive to further increases in temperature than it was even 50 years ago.”
One noteworthy aspect of the findings, Das said, was how little additional warming it now takes to cause huge spikes in ice sheet melting.
“Even a very small change in temperature caused an exponential increase in melting in recent years,” she said. “So the ice sheet’s response to human-caused warming has been non-linear.” Trusel concluded, “Warming means more today than it did in the past.”
Additional co-authors are: Matthew B. Osman, MIT/WHOI Joint Program in Oceanography; Matthew J. Evans, Wheaton College; Ben E. Smith, University of Washington; Xavier Fettweis, University of Leige; Joseph R. McConnell, Desert Research Institute; and Brice P. Y. Noël and and Michiel R. van den Broeke Utrecht University.
This research was funded by the US National Science Foundation, institutional support from Rowan University and Woods Hole Oceanographic Institution, the US Department of Defense, the Netherlands Organization for Scientific Research, the Netherlands Earth System Science Center, and the Belgian National Fund for Scientific Research.
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Link to paper (on and after Dec. 5, 2018): https://doi.org/10.1038/s41586-018-0752-4
News media contacts:
WHOI Media Office- 508-289-3340, media@whoi.edu
Sarah Das, Ph.D., Woods Hole Oceanographic Institution (508) 289-2464 (office), sdas@whoi.edu https://www2.whoi.edu/staff/sdas/
Stephen Levine, News Officer, University Relations, Rowan University(856) 256-5443 (office), (856) 889-0491 (cell), Levines@Rowan.edu
Luke Trusel, Ph.D., School of Earth & Environment, Rowan University (856) 256 5262 (office), (508) 981-3073 (cell), trusel@rowan.edu, https://cryospherelab.org
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.
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
Nov 13, 2018 | News releases, Research findings
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. 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. 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.
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.
May 14, 2018 | News releases, Research findings
Dr. Monica Arienzo inspects an ice core sample in the ice core lab at the Desert Research Institute in Reno, Nev. Photo credit: DRI.
Reno, NV (May 14, 2018): To learn about the rise and fall of ancient European civilizations, researchers sometimes find clues in unlikely places: deep inside of the Greenland ice sheet, for example.
Thousands of years ago, during the height of the ancient Greek and Roman empires, lead emissions from sources such as the mining and smelting of lead-silver ores in Europe drifted with the winds over the ocean to Greenland – a distance of more than 2800 miles (4600 km) – and settled onto the ice. Year after year, as fallen snow added layers to the ice sheet, lead emissions were captured along with dust and other airborne particles and became part of the ice-core record that scientists use today to learn about conditions of the past.
In a new study published in PNAS, a team of scientists, archaeologists and economists from the Desert Research Institute (DRI), the University of Oxford, NILU – Norwegian Institute for Air Research and the University of Copenhagen used ice samples from the North Greenland Ice Core Project (NGRIP) to measure, date and analyze European lead emissions that were captured in Greenland ice between 1100 BC and AD 800. Their results provide new insight for historians about how European civilizations and their economies fared over time.
“Our record of sub-annually resolved, accurately dated measurements in the ice core starts in 1100 BC during the late Iron Age and extends through antiquity and late antiquity to the early Middle Ages in Europe – a period that included the rise and fall of the Greek and Roman civilizations,” said the study’s lead author Joe McConnell, Ph.D., Research Professor of Hydrology at DRI. “We found that lead pollution in Greenland very closely tracked known plagues, wars, social unrest and imperial expansions during European antiquity.”
Map showing location of NGRIP ice core in relation to Roman lead/silver mines. Credit: DRI.
A previous study from the mid-1990s examined lead levels in Greenland ice using only 18 measurements between 1100 BC and AD 800; the new study provides a much more complete record that included more than 21,000 precise lead and other chemical measurements to develop an accurately dated, continuous record for the same 1900-year period.
To determine the magnitude of European emissions from the lead pollution levels measured in the Greenland ice, the team used state-of-the-art atmospheric transport model simulations.
“We believe this is the first time such detailed modeling has been used to interpret an ice-core record of human-made pollution and identify the most likely source region of the pollution,” said co-author Andreas Stohl, Ph.D., Senior Scientist at NILU.
Most of the lead emissions from this time period are believed to have been linked to the production of silver, which was a key component of currency.
“Because most of the emissions during these periods resulted from mining and smelting of lead-silver ores, lead emissions can be seen as a proxy or indicator of overall economic activity,” McConnell explained.
Using their detailed ice-core chronology, the research team looked for linkages between lead emissions and significant historical events. Their results show that lead pollution emissions began to rise as early as 900 BC, as Phoenicians expanded their trading routes into the western Mediterranean. Lead emissions accelerated during a period of increased mining activity by the Carthaginians and Romans primarily in the Iberian Peninsula and reached a maximum under the Roman Empire.
Chronology of European lead emissions that were captured in Greenland ice between 1100 BC and AD 800 in relation to major historic events. Credit: DRI.
The team’s extensive measurements provide a different picture of ancient economic activity than previous research had provided. Some historians, for example, had argued that the sparse Greenland lead record provided evidence of better economic performance during the Roman Republic than during the Roman Empire.
According to the findings of this study, the highest sustained levels of lead pollution emissions coincided with the height of the Roman Empire during the 1st and 2nd centuries AD, a period of economic prosperity known as the Pax Romana. The record also shows that lead emissions were very low during the last 80 years of the Roman Republic, a period known as the Crisis of the Roman Republic.
“The nearly four-fold higher lead emissions during the first two centuries of the Roman Empire compared to the last decades of the Roman Republic indicate substantial economic growth under Imperial rule,” said coauthor Andrew Wilson, Professor of the Archaeology of the Roman Empire at Oxford.
The team also found that lead emissions rose and fell along with wars and political instability, particularly during the Roman Republic, and took sharp dives when two major plagues struck the Roman Empire in the 2nd and 3rd centuries. The first, called the Antonine Plague, was probably smallpox. The second, called the Plague of Cyprian, struck during a period of political instability called the third-century crisis.
“The great Antonine Plague struck the Roman Empire in AD 165 and lasted at least 15 years. The high lead emissions of the Pax Romana ended exactly at that time and didn’t recover until the early Middle Ages more than 500 years later,” Wilson explained.
The research team for this study included ice-core specialists, atmospheric scientists, archaeologists, and economic historians – an unusual combination of expertise.
“Working with such a diverse team was a unique experience in my career as a scientist,” McConnell said. “I think that our results show that there can be great value in collaborating across disciplines.”
Analysis and interpretation of archived NGRIP2 ice-core samples were supported by the John Fell Oxford University Press Research Fund and All Souls College, Oxford, as well as the Desert Research Institute.
The project team included an interdisciplinary team of researchers, including (left to right) Dr. Audrey Yau, ice core specialist and former DRI post-doc; Dr. Monica Arienzo, ice core specialist, DRI; Elisabeth Thompson, doctoral student, Oxford University; Professor Andrew Wilson, historian, Oxford University; and Professor Joe McConnell, ice core specialist, DRI.
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.
