Large wildfires have raged across the western Americas in the past decade including the Las Conchas, New Mexico fire that burned 44,000 acres in a single day in 2011 (Orem and Pelletier, 2015, Geomorphology 232: 224-238, and references therein), the 2016 Fort McMurray, Alberta fire that required evacuating an entire city, and the 2015 Alaskan fire season that burned more than 5 million acres (Alaska Interagency Coodination Center). These fires are caused by a changing climate resulting in hotter, drier conditions across much of the western North America, and are augmented by land-use practices resulting in more potential forest fuel. It is essential to place these fires in a longer temporal context to examine if recent fires are anomalous or if they have occurred in the past under diverse climate conditions.
Recent peat fires in Indonesia demonstrate that biomass burning causes carbon dioxide emissions that can be as much as 50% of those from fossil-fuel combustion and so are highly likely to influence future climate change (Stocker, and others, 2013, Technical Summary, in Climate Change 2013: The Physical Science Basis: Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change: Cambridge University Press; Global Fire Emissions Database) However, aerosols—and especially fire aerosols—continue to be one of the least understood aspects of the modern climate system and even less is known about their past influence (Stocker, and others, 2013). The impact of these aerosols when they fall back to the surface is unknown. Wildfire aerosols may accelerate glacier melt through depositing dark material on reflective glaciers, thereby decreasing the glacier's albedo. The effect of fire aerosols on the water quality local and regional watersheds is also not well known.
Project Lead Natalie Kehrwald and collaborators developed methods to determine molecular markers of fire activity in ice and lake cores (e.g. Gambaro and others 2008, Analytical Chemistry 80 (5), 1649–1655; Kehrwald and others, 2012, Tellus Series B – Chemical and Physical Meteorology, 64, 18196; Zennaro and others, 2014, Climate of the Past, 10, 5, 1905-1924 and Zennaro and others, 2015, Geophysical Research Letters, 42, 12, 5023-5033). Levoglucosan is a specific biomarker in that it can only be produced by cellulose burning at temperatures centered around ~250°C (Kuo and others, 2011, Chemosphere, 85, 5, 797-805). Levoglucosan is incorporated into smoke plumes, transported in the atmosphere, and deposited through wet and dry deposition. The presence of levoglucosan can be used to determine fire histories in paleoclimate records through the Holocene (Zennaro and others, 2014 and Zennaro and others, 2015). High resolution records of levoglucosan in short ice cores can indicate whether fire aerosols are accelerating glacier melt. Investigating levoglucosan concentrations in modern streams can help determine if fire aerosols affect surface water quality.
Humans have had control over fire for at least the last 1 million years (Berna and others, 2012, PNAS, 109, 20, E1215-E1220). This "control" is relative, however, as human ignitions can accidentally cause wildfires such as the 2016 Nederland, Colorado fire that started from an improperly doused campfire. In areas that are not naturally fire-prone, biomass burning residue in lake cores is sometimes used as an indicator of the presence of humans in an area. New techniques using specific biomarkers can determine if and when humans lived in a region, and if the presence of humans coincides with increased fire activity.
However, specific biomarkers can help determine the timing and interpretation of climatic and anthropogenic events. For example, changing climate conditions coupled with deforestation, enforced agriculture and/or pastoralism, and the introduction of European diseases may have influenced the ability of residents to continue living in the mountains of northern New Mexico. Fecal sterols indicate the presence of humans in an area, and by investigating these markers in tandem with levoglucosan (Battistel and others, 2015, Analytical and Bioanalytical Chemistry, 28, 8505-8514) the interactions and impacts of fire, climate, and human activity in a region such as northern New Mexico can be reconstructed.
The climate of the southwestern U.S. is projected to become hotter and drier in the upcoming decades, mirroring climate conditions that lead in part to the decline of civilizations such as the one in Chaco Canyon. Lake core records can help establish the roles of humans and climate in such societal shifts. The investigation of organic tracers is expanding the limits of proxy information and provides data for one of the least understood aspects of the climate system, with implications for how past societies responded to a changing climate.
Objectives
This project investigates the interactions between a warming climate, increasing fire activity and impacts on people initially by addressing the following questions:
- Are recent wildfires accelerating the melt of the Juneau Icefield or other glaciers?
Biomass burning deposits aerosols on snow surfaces. Dark aerosols from fossil fuel burning are known to increase glacier surface melt over sub-seasonal timescales, yet the effect of wildfire aerosols on glacier surfaces is currently unknown. We are collecting data on levoglucosan concentrations in short (7-9 meter) snow cores from the Juneau Icefield in conjunction with stable isotopes, major ions, and dust concentrations to determine if and how wildfire aerosols affect surface melt relative to other factors such as warmer temperatures and increased dust deposition.
- What role did climate and land use change associated with burning vegetation play in the human history of northern New Mexico?
Humans have used fire for thousands of years for land clearance in northern New Mexico. With the arrival of Europeans, and associated increased pastoralism and enforced agriculture, the relationship between human activity and fire changed across much of the southwestern U.S. Regions that were converted to intense pastoralism may not have supported sufficient vegetation for large fires. Population changes and shifting settlement areas can alter fire activity in specific localities that differ from trends in fire activity across the southwestern U.S. as a whole. Data from lake cores demonstrate the changing vegetation in the region, but currently do not include specific markers for determining the presence of humans. Investigating fecal sterols as a marker of human presence in northern New Mexico sediment cores can specifically determine when people lived in an area. We are drilling new lake cores, as well as investigating fecal sterols and levoglucosan in existing sediment cores to provide a value-added component to previous USGS studies.
Sampling
In July and August, 2016 and 2017 Natalie Kehrwald (USGS GECSC), Sarah Fortner (Wittenberg University), Shad O’Neel and Chris McNeil (USGS), and teams of students used a Kovacs drill to obtain a transect of 7 to 9 meter cores across the Juneau Icefield, Alaska. This project is a joint effort with the Juneau Icefield Research Program (JIRP). We sincerely thank all JIRP students and staff for their efforts in making this work possible.
Applicability
Chemical markers provide fire data across a wide array of time scales and types of information. These biomarkers are especially valuable as they are present in both ice and lake cores. We use levoglucosan, and its isomers mannosan and galactosan, to reconstruct past fire history from ice cores and lake sediments.
Our previous research demonstrates the applicability of using levoglucosan in ice cores to determine past biomass burning and the role of humans in altering fire activity (figure below). The NEEM, Greenland ice core contains fire biomarkers throughout the Holocene. The peak in fire activity centered around ~2500 years before present cannot be explained by climate variables such as increased temperature or summer insolation. Model results for the potential source areas do not show an increase in area burnt unless human activity is taken into account. We ascribe this peak fire activity to land clearance for agriculture (see Zennaro and others, 2015 for full details).
One of the most enticing questions in fire science is determining how fires ignited. Defining if a natural ignition such as lightning or human ignition such as an out-of-control campfire caused a wildfire is currently not possible. However, biomarkers such as fecal sterols provide direct proof that humans were in an area. Combining the presence of fecal sterols with levoglucosan can show the presence of humans in a local area and any possible correction with changes in fire activity (Battistel and others, 2016, The Holocene, 1-11).

Laboratory Methods
Through a collaboration with Larry Barber and Jeramy Jasmann (National Research Program, Boulder, Colorado), new methods are being developed to determine the specific fire biomarkers levoglucosan, mannosan and galactoan in ice and lake cores using a gas chromatography coupled to tandem mass spectrometry. This method allows for separating levoglucosan and its isomers as well as using initial sample sizes of 1 mL or less. Current methods for determining levoglucosan in snow and ice use different instrumentation that may not be able to separate levoglucosan from its isomers, or may use a larger initial sample (Gambaro and others, 2008, Analytical Chemistry 80 (5), 1649–1655; Kuo and others, 2011; You and others, 2016, Talanta, 148, 534-538). This collaborative work is expanding the fire history methods to incorporate analysis of fecal sterols in lake sediments in order to determine both biomass burning and the presence of humans (Battistel and others, 2015).
Below are data or web applications associated with this project.
Investigating fire frequency and vegetative combustion sources using wildland fire tracer molecules archived in the Juneau Icefield of Alaska
The publications on this page represents current research conducted by the Geosciences and Environmental Change Science Center since 2016. For earlier publications on this subject by Natalie Kehrwald and colleagues, please refer to her USGS Staff Profile.
Dissolved organic matter in the deep TALDICE ice core: A nano-UPLC-nano-ESI-HRMS method
PaCTS 1.0: A crowdsourced reporting standard for paleoclimate data
Fire, vegetation, and Holocene climate in a southeastern Tibetan lake: a multi-biomarker reconstruction from Paru Co
Global Modern Charcoal Dataset (GMCD): A tool for exploring proxy-fire linkages and spatial patterns of biomass burning
Lake sediment fecal and biomass burning biomarkers provide direct evidence for prehistoric human-lit fires in New Zealand
High latitude Southern Hemisphere fire history during the mid-late Holocene (750- 6000 yr BP)
A North American Hydroclimate Synthesis (NAHS) of the Common Era
Anthropogenic impact in the Mayan Lowlands of Petén, Guatemala, during the last 5500 years
Prospects for reconstructing paleoenvironmental conditions from organic compounds in polar snow and ice
One thousand years of fires: Integrating proxy and model data
Fire in the Earth System: Bridging data and modeling research
- Overview
Large wildfires have raged across the western Americas in the past decade including the Las Conchas, New Mexico fire that burned 44,000 acres in a single day in 2011 (Orem and Pelletier, 2015, Geomorphology 232: 224-238, and references therein), the 2016 Fort McMurray, Alberta fire that required evacuating an entire city, and the 2015 Alaskan fire season that burned more than 5 million acres (Alaska Interagency Coodination Center). These fires are caused by a changing climate resulting in hotter, drier conditions across much of the western North America, and are augmented by land-use practices resulting in more potential forest fuel. It is essential to place these fires in a longer temporal context to examine if recent fires are anomalous or if they have occurred in the past under diverse climate conditions.
Dark aerosols from recent wildfires may increase the melting of the Juneau Icefield. Recent peat fires in Indonesia demonstrate that biomass burning causes carbon dioxide emissions that can be as much as 50% of those from fossil-fuel combustion and so are highly likely to influence future climate change (Stocker, and others, 2013, Technical Summary, in Climate Change 2013: The Physical Science Basis: Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change: Cambridge University Press; Global Fire Emissions Database) However, aerosols—and especially fire aerosols—continue to be one of the least understood aspects of the modern climate system and even less is known about their past influence (Stocker, and others, 2013). The impact of these aerosols when they fall back to the surface is unknown. Wildfire aerosols may accelerate glacier melt through depositing dark material on reflective glaciers, thereby decreasing the glacier's albedo. The effect of fire aerosols on the water quality local and regional watersheds is also not well known.
Project Lead Natalie Kehrwald and collaborators developed methods to determine molecular markers of fire activity in ice and lake cores (e.g. Gambaro and others 2008, Analytical Chemistry 80 (5), 1649–1655; Kehrwald and others, 2012, Tellus Series B – Chemical and Physical Meteorology, 64, 18196; Zennaro and others, 2014, Climate of the Past, 10, 5, 1905-1924 and Zennaro and others, 2015, Geophysical Research Letters, 42, 12, 5023-5033). Levoglucosan is a specific biomarker in that it can only be produced by cellulose burning at temperatures centered around ~250°C (Kuo and others, 2011, Chemosphere, 85, 5, 797-805). Levoglucosan is incorporated into smoke plumes, transported in the atmosphere, and deposited through wet and dry deposition. The presence of levoglucosan can be used to determine fire histories in paleoclimate records through the Holocene (Zennaro and others, 2014 and Zennaro and others, 2015). High resolution records of levoglucosan in short ice cores can indicate whether fire aerosols are accelerating glacier melt. Investigating levoglucosan concentrations in modern streams can help determine if fire aerosols affect surface water quality.
Interactions between glaciers, bedrock, and surface debris on the Gilkey Glacier, Juneau Icefield, Alaska. An ideal ice core site is the highest, flattest glacier in a region. In 2016, a transect of 7-9 m ice cores was drilled on the Matthes Glacier, Juneau Icefield to determine if recent fires are affecting the glacier surface. Humans have had control over fire for at least the last 1 million years (Berna and others, 2012, PNAS, 109, 20, E1215-E1220). This "control" is relative, however, as human ignitions can accidentally cause wildfires such as the 2016 Nederland, Colorado fire that started from an improperly doused campfire. In areas that are not naturally fire-prone, biomass burning residue in lake cores is sometimes used as an indicator of the presence of humans in an area. New techniques using specific biomarkers can determine if and when humans lived in a region, and if the presence of humans coincides with increased fire activity.
However, specific biomarkers can help determine the timing and interpretation of climatic and anthropogenic events. For example, changing climate conditions coupled with deforestation, enforced agriculture and/or pastoralism, and the introduction of European diseases may have influenced the ability of residents to continue living in the mountains of northern New Mexico. Fecal sterols indicate the presence of humans in an area, and by investigating these markers in tandem with levoglucosan (Battistel and others, 2015, Analytical and Bioanalytical Chemistry, 28, 8505-8514) the interactions and impacts of fire, climate, and human activity in a region such as northern New Mexico can be reconstructed.
The climate of the southwestern U.S. is projected to become hotter and drier in the upcoming decades, mirroring climate conditions that lead in part to the decline of civilizations such as the one in Chaco Canyon. Lake core records can help establish the roles of humans and climate in such societal shifts. The investigation of organic tracers is expanding the limits of proxy information and provides data for one of the least understood aspects of the climate system, with implications for how past societies responded to a changing climate.
Objectives
The rapidly degrading Llewellyn Glacier, Juneau Icefield. This project investigates the interactions between a warming climate, increasing fire activity and impacts on people initially by addressing the following questions:
- Are recent wildfires accelerating the melt of the Juneau Icefield or other glaciers?
Biomass burning deposits aerosols on snow surfaces. Dark aerosols from fossil fuel burning are known to increase glacier surface melt over sub-seasonal timescales, yet the effect of wildfire aerosols on glacier surfaces is currently unknown. We are collecting data on levoglucosan concentrations in short (7-9 meter) snow cores from the Juneau Icefield in conjunction with stable isotopes, major ions, and dust concentrations to determine if and how wildfire aerosols affect surface melt relative to other factors such as warmer temperatures and increased dust deposition.
- What role did climate and land use change associated with burning vegetation play in the human history of northern New Mexico?
Humans have used fire for thousands of years for land clearance in northern New Mexico. With the arrival of Europeans, and associated increased pastoralism and enforced agriculture, the relationship between human activity and fire changed across much of the southwestern U.S. Regions that were converted to intense pastoralism may not have supported sufficient vegetation for large fires. Population changes and shifting settlement areas can alter fire activity in specific localities that differ from trends in fire activity across the southwestern U.S. as a whole. Data from lake cores demonstrate the changing vegetation in the region, but currently do not include specific markers for determining the presence of humans. Investigating fecal sterols as a marker of human presence in northern New Mexico sediment cores can specifically determine when people lived in an area. We are drilling new lake cores, as well as investigating fecal sterols and levoglucosan in existing sediment cores to provide a value-added component to previous USGS studies.
Sampling
In July and August, 2016 and 2017 Natalie Kehrwald (USGS GECSC), Sarah Fortner (Wittenberg University), Shad O’Neel and Chris McNeil (USGS), and teams of students used a Kovacs drill to obtain a transect of 7 to 9 meter cores across the Juneau Icefield, Alaska. This project is a joint effort with the Juneau Icefield Research Program (JIRP). We sincerely thank all JIRP students and staff for their efforts in making this work possible.
Location of the Juneau Icefield in relation to other Alaskan glaciers. (Map background: ESRI World Imagery) Molly Peek and Chris Miele drilling and processing firn cores on the Juneau Icefield, Alaska. Applicability
Chemical markers provide fire data across a wide array of time scales and types of information. These biomarkers are especially valuable as they are present in both ice and lake cores. We use levoglucosan, and its isomers mannosan and galactosan, to reconstruct past fire history from ice cores and lake sediments.
Our previous research demonstrates the applicability of using levoglucosan in ice cores to determine past biomass burning and the role of humans in altering fire activity (figure below). The NEEM, Greenland ice core contains fire biomarkers throughout the Holocene. The peak in fire activity centered around ~2500 years before present cannot be explained by climate variables such as increased temperature or summer insolation. Model results for the potential source areas do not show an increase in area burnt unless human activity is taken into account. We ascribe this peak fire activity to land clearance for agriculture (see Zennaro and others, 2015 for full details).
One of the most enticing questions in fire science is determining how fires ignited. Defining if a natural ignition such as lightning or human ignition such as an out-of-control campfire caused a wildfire is currently not possible. However, biomarkers such as fecal sterols provide direct proof that humans were in an area. Combining the presence of fecal sterols with levoglucosan can show the presence of humans in a local area and any possible correction with changes in fire activity (Battistel and others, 2016, The Holocene, 1-11).
Sources/Usage: Some content may have restrictions. Visit Media to see details.Greenland ice core records fire activity over thousands of years. Levoglucosan concentrations indicate peak biomass burning occurring ~2500 years before present where this increased combustion occurs separately from associated climate variables such as temperature (see Zennaro and others, 2015 for full details. Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)). Laboratory Methods
Through a collaboration with Larry Barber and Jeramy Jasmann (National Research Program, Boulder, Colorado), new methods are being developed to determine the specific fire biomarkers levoglucosan, mannosan and galactoan in ice and lake cores using a gas chromatography coupled to tandem mass spectrometry. This method allows for separating levoglucosan and its isomers as well as using initial sample sizes of 1 mL or less. Current methods for determining levoglucosan in snow and ice use different instrumentation that may not be able to separate levoglucosan from its isomers, or may use a larger initial sample (Gambaro and others, 2008, Analytical Chemistry 80 (5), 1649–1655; Kuo and others, 2011; You and others, 2016, Talanta, 148, 534-538). This collaborative work is expanding the fire history methods to incorporate analysis of fecal sterols in lake sediments in order to determine both biomass burning and the presence of humans (Battistel and others, 2015).
2016 Glacial Biogeochemistry Team: Front row (left to right): Sarah Fortner, Kiana Ziola, Auri Clark, Natalie Kehrwald. Back row (left to right): Kristen Aruell, Chris Miele, Annie Zaccharin, Kit Cunningham, Annie Holt, Molly Peek. - Are recent wildfires accelerating the melt of the Juneau Icefield or other glaciers?
- Data
Below are data or web applications associated with this project.
Investigating fire frequency and vegetative combustion sources using wildland fire tracer molecules archived in the Juneau Icefield of Alaska
The past decade includes some of the most extensive boreal forest fires in the historical record. Environmental drivers include warming temperatures, changing precipitation patterns, desiccation of thick organic soil layers, and increased ignition frequency from lightning. Wildland fires produce smoke aerosols that can travel thousands of kilometers, before blanketing the surfaces on which they fa - Publications
The publications on this page represents current research conducted by the Geosciences and Environmental Change Science Center since 2016. For earlier publications on this subject by Natalie Kehrwald and colleagues, please refer to her USGS Staff Profile.
Dissolved organic matter in the deep TALDICE ice core: A nano-UPLC-nano-ESI-HRMS method
Trace organic compounds in deep ice cores supply important paleoclimatic information. Untargeted analyses of dissolved organic matter provide an overview of molecular species in ice samples however, sample volumes usually required for these analyses are generally not available from deep ice cores. Here, we developed an analytical method using a nano-UPLC-nano-ESI-HRMS to detect major molecular speAuthorsRoberta Zangrando, Veronica Zanella, Ornela Karroca, Elena Barbaro, Natalie Kehrwald, Dario Battistel, Andrea Gambaro, Carlo BarbantePaCTS 1.0: A crowdsourced reporting standard for paleoclimate data
The progress of science is tied to the standardization of measurements, instruments, and data. This is especially true in the Big Data age, where analyzing large data volumes critically hinges on that data being standardized. Accordingly, the lack of community-sanctioned data standards in paleoclimatology has largely precluded the benefits of Big Data advances in the field. Building upon recent efAuthorsNatalie M. Kehrwald, Deborah Khider, Julien Emile-Geay, Nicholas P. McKay, Yolanda Gili, Daniel Garijo, Varun Ratnakar, Peter Brewer, Adam Csank, Emilie Dassie, Kristine Delong, Thomas Felix, William Gray, Lucas Jonkers, Michael Kahle, Darrell S. Kaufman, Julie N. Richey, Andreas Schmittner, Elaine Kennedy Sutherland, Montserrat Alonso-Garcia, Bertrand Sebastian, Oliver Bothe, Andrew Bunn, Manuel Chevalier, Pierre Francus, Amy Frappier, Simon Goring, Belen Martrat, Helen V. McGregor, Kathryn J. Allen, Fabien Arnaud, Yarrow L. Axford, Timothy T. Barrows, Lucie Bazin, S.E. Pilaar Birch, Elizabeth Bradley, Joshua Bregy, Emilie Capron, Olivier Cartapanis, Hong-Wei Chiang, Kim Cobb, Maxime Debret, Rene Dommain, Jianghui Du, Kelsey Dyez, Suellyn Emerick, Michael Erb, Georgina Falster, Walter Finsinger, Daniel Fortier, Nicolas Gauthier, Steven George, Eric Grimm, Jennifer Hertzberg, Fiona Hibbert, Aubrey Hillman, William Hobbs, Matthew Huber, Anna L. C. Hughes, Samuel Jaccard, Ruan Jiaoyang, Markus Kienast, Bronwen Konecky, Gael Le Roux, Vyacheslav Lyubchich, Valdir Novello, Lydia Olaka, Judson W. Partin, Christof Pearce, Steven J. Phipps, Cecile Pignol, Natalia Pietrowska, Maria-Serena Poli, Alexander Prokopenko, Franciele Schwanck, Christian Stepanek, George E. A. Swann, Richard Telford, Elizabeth R. Thomas, Zoe Thomas, Sarah Truebe, Lucien von Gunten, Amanda Waite, Nils Weitzel, Bruno Wilhelm, John B. Williams, Mai Winstrup, Ning Zhao, Yuxin ZhouFire, vegetation, and Holocene climate in a southeastern Tibetan lake: a multi-biomarker reconstruction from Paru Co
The fire history of the Tibetan Plateau over centennial to millennial timescales is not well known. Recent ice core studies reconstruct fire history over the past few decades but do not extend through the Holocene. Lacustrine sedimentary cores, however, can provide continuous records of local environmental change on millennial scales during the Holocene through the accumulation and preservation ofAuthorsAlice Callergaro, Dario Battistel, Natalie M. Kehrwald, Felipe Matsubara Pereira, Torben Kirchgeorg, Maria del Carmen Villoslada Hidalgo, Broxton W. Bird, Carlo BarbanteGlobal Modern Charcoal Dataset (GMCD): A tool for exploring proxy-fire linkages and spatial patterns of biomass burning
Progresses in reconstructing Earth's history of biomass burning has motivated the development of a modern charcoal dataset covering the last decades through a community-based initiative called the Global Modern Charcoal Dataset (GMCD). As the frequency, intensity and spatial scale of fires are predicted to increase regionally and globally in conjunction with changing climate, anthropogenic activitAuthorsDonna Hawthorne, Colin J. Courtney Mustaphi, Julie C. Aleman, Olivier Blarquez, Daniele Colombaroli, Anne-Laure Daniau, Jennifer R. Marlon, Mitchell Power, Boris Vanniere, Youngming Han, Stijn Hantson, Natalie M. Kehrwald, Brian I. Magi, Xu Yue, Christopher Carcaillet, Rob Marchant, Ayodele Ogunkoya, Esther N. Githumbi, Rebecca M. MuriukiLake sediment fecal and biomass burning biomarkers provide direct evidence for prehistoric human-lit fires in New Zealand
Deforestation associated with the initial settlement of New Zealand is a dramatic example of how humans can alter landscapes through fire. However, evidence linking early human presence and land-cover change is inferential in most continental sites. We employed a multi-proxy approach to reconstruct anthropogenic land use in New Zealand’s South Island over the last millennium using fecal and plantAuthorsElena Argiriadis, Dario Battistel, David B. McWethy, Marco Vecchiato, Torben Kirchgeorg, Natalie M. Kehrwald, Cathy Whitlock, Janet M. Wilmshurst, Carlo BarbanteHigh latitude Southern Hemisphere fire history during the mid-late Holocene (750- 6000 yr BP)
We determined the specific biomass burning biomarker levoglucosan in an ice core from the TALos Dome Ice CorE drilling project (TALDICE) during the mid- to late Holocene (6000–750 BP). The levoglucosan record is characterized by a long-term increase with higher rates starting at ∼ 4000 BP and peaks between 2500 and 1500 BP. The anomalous increase in levoglucosan centered at ∼ 2000 BP is consisAuthorsDario Battistel, Natalie M. Kehrwald, Piero Zennaro, Giuseppe Pellegrino, Elena Barbaro, Roberta Zangrando, Xanthi X. Pedeli, Cristiano Varin, Andrea Spolaor, Paul T. Vallelonga, Andrea Gambaro, Carlo BarbanteA North American Hydroclimate Synthesis (NAHS) of the Common Era
This study presents a synthesis of century-scale hydroclimate variations in North America for the Common Era (last 2000 years) using new age models of previously published multiple proxy-based paleoclimate data. This North American Hydroclimate Synthesis (NAHS) examines regional hydroclimate patterns and related environmental indicators, including vegetation, lake water elevation, stream flow andAuthorsJessica R. Rodysill, Lesleigh Anderson, Thomas M. Cronin, Miriam C. Jones, Robert S. Thompson, David B. Wahl, Debra A. Willard, Jason A. Addison, Jay R. Alder, Katherine H. Anderson, Lysanna Anderson, John A. Barron, Christopher E. Bernhardt, Steven W. Hostetler, Natalie M. Kehrwald, Nicole Khan, Julie N. Richey, Scott W. Starratt, Laura E. Strickland, Michael Toomey, Claire C. Treat, G. Lynn WingardByWater Resources Mission Area, Climate Research and Development Program, Energy Resources Program, Groundwater and Streamflow Information Program, Mineral Resources Program, National Laboratories Program, Science and Decisions Center, Florence Bascom Geoscience Center, Geology, Minerals, Energy, and Geophysics Science Center, Geosciences and Environmental Change Science Center, St. Petersburg Coastal and Marine Science CenterAnthropogenic impact in the Mayan Lowlands of Petén, Guatemala, during the last 5500 years
Trace and rare earth elements from a Lake Peten Itzá (Guatemala) sediment core depict the geochemical dynamics affecting the lake from ~5500 y BP to the present. This timing encompasses the Preclassic (4000 to 1700 y BP) and Classic Periods (1700-1000 y BP) when thriving Maya societies extensively cleared land for agriculture. We demonstrate that this land use occurred during times of increased prAuthorsD. Battistel, Marco Roman, A Marchetti, Natalie M. Kehrwald, Marta Radaelli, Eleanora Balliana, Giuseppina Toscano, Carlo BarbanteProspects for reconstructing paleoenvironmental conditions from organic compounds in polar snow and ice
Polar ice cores provide information about past climate and environmental changes over periods ranging from a few years up to 800,000 years. The majority of chemical studies have focused on determining inorganic components, such as major ions and trace elements as well as on their isotopic fingerprint. In this paper, we review the different classes of organic compounds that might yield environmentaAuthorsChiara Giorio, Natalie M. Kehrwald, Carlo Barbante, Markus Kalberer, Amy C.F. King, Elizabeth R. Thomas, Eric W. Wolff, Piero ZennaroOne thousand years of fires: Integrating proxy and model data
The current fires raging across Indonesia are emitting more carbon than the annual fossil fuel emissions of Germany or Japan, and the fires are still consuming vast tracts of rainforest and peatlands. The National Interagency Fire Center (www.nifc.gov) notes that 2015 is one worst fire years on record in the U.S., where more than 9 million acres burned -- equivalent to the combined size of MassachAuthorsNatalie M. Kehrwald, Julie C. Aleman, Michael Coughlan, Colin J. Courtney Mustaphi, Esther N. Githumbi, Brian I. Magi, Jennifer R. Marlon, Mitchell J. PowerFire in the Earth System: Bridging data and modeling research
Significant changes in wildfire occurrence, extent, and severity in areas such as western North America and Indonesia in 2015 have made the issue of fire increasingly salient in both the public and scientific spheres. Biomass combustion rapidly transforms land cover, smoke pours into the atmosphere, radiative heat from fires initiates dramatic pyrocumulus clouds, and the repeated ecological and atAuthorsSrijn Hantson, Silvia Kloster, Michael Coughlan, Anne-Laure Daniau, Boris Vanniere, Tim Bruecher, Natalie M. Kehrwald, Brian I. Magi