Darrell Kaufman – Quaternary geology and paleoclimatology

My research group studies geologic records of environmental changes to understand how the Earth system responds to natural and anthropogenic forcings on millennial time scales. We focus on lake sediments from Alaska, geochronology, and proxy climate syntheses.

Regents’ Professor
School of Earth and Sustainability
Northern Arizona University
Bury Hall, Building 8, rm 306; 928-523-7192
Email: darrell.kaufman@nau.edu
Twitter: https://twitter.com/DKaufman1

Large-scale climate indicators from Chapter 2 of the IPCC Sixth Assessment Report quantifying their current state compare with the past

Publications
Google Scholar
Full list

Laboratories
Amino Acid Geochronology (AAGL)
Sedimentary Records of Environmental Change
Arizona Climate and Ecosystems (ACE) Isotope Lab (radiocarbon)

Projects
Arctic Glacial Lakes
South Alaska Lakes

More at
Past and Present Climate Change, School of Earth & Sustainability
Taking Earth’s Temperature -Delving into Climate’s Past, NAU Documentary
Reports from the field, Polar Field Services
Core Curriculum, Pine, NAU Alumni Association magazine

Curriculum vitae (brief)

Research

To understand environmental change and its current trajectory requires a long-term perspective of the natural variability in the Earth system. My group studies lake and glacial deposits that provide an archive of long-term climate variability. Our field-oriented projects are mainly in Alaska where past and ongoing climate changes have been pronounced and future changes are anticipated to be greatest. In the lab, we analyze the physical properties of lake sediments to reconstruct past climate change and we use radiocarbon, amino acids, and tephras to place these records on a timeline.

Lake Sediments from Alaska

Anne & Dave with sediment core from Adak Island

Sediments that accumulate in lakes contain a wealth of information about past and present environmental changes. My group collects sediment cores from lakes and analyzes them for a variety of physical and biological properties. In addition to the analytical equipment in the Sedimentary Records of Environmental Change Lab at NAU, we collaborate with the Continental Scientific Drilling Facility and other laboratories for various analyses.

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Al & Scott assemble weather station, Long Lake, Copper R basin

In southern Alaska we are using annually bedded sediment from glacier-fed lakes and isotopes and productivity indicators from non-glacial lakes to interpret climatic changes, glacier fluctuations and floods.

In Arctic Alaska and elsewhere we are monitoring the rivers and lakes, along with the weather, to inform our interpretations of sedimentary sequences stored by the lakes, including those that relate to Arctic sea ice and to summer temperature.

We integrate our studies into larger international syntheses of lacustrine-based paleoenvironmental records internationally.

Quaternary Geochronology

Because knowing the ages of sedimentary sequences and their constituents is essential to understanding the timing, rate, and regional extent of past environmental changes, my group has a strong emphasis in geochronology. Specialties include:

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Amino acid geochronology

The technique is used to determine the approximate ages of carbonate-based fossils as old as several million years. Recent applications in the Amino Acid Geochronology Laboratory include Arctic Ocean sediment cores, conservation paleobiology, time-averaging of the fossil record, tectonic geomorphology, methodological advancements, among many others.

Radiocarbon

NAU’ s ACE Lab is the first university lab in the US with a Mini Carbon Dating System (MICADAS), the latest technology for analyzing radiocarbon. Very small samples can be analyzed with the gas-ion source. We use radiocarbon extensively to date our lake sediment cores, sometimes in combination of tephras, and to calibrate the rate of amino acid reactions.

Tephrochronology

All of the lakes that we study in Alaska contain volcanic ash layers from frequent eruptions of Aleutian Arc volcanoes including as cryptotephra. We collaborate with tephra specialists at University of Alberta and elsewhere to document the regional tephra sequences and their sources and have used tephra to validate the accuracy of radiocarbon-based age models, including their error estimates.

Paleoclimate Data Syntheses

Temp12k global temperature reconstruction

The paleoclimate group at NAU is leading collaborative projects to assemble large, reusable datasets of proxy climate records to study past global climate changes. These data products have been used to place recent changes in a long-term context, reconstruct the latitudinal temperature gradient of the Northern Hemisphere, determine the onset of Neoglacial cooling, evaluate climate model performance, and to quanitfy natural climate variability. Crafting the large datasets for these projects requires a major effort in science coordination and data stewardship.

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For the Holocene, the Temp12k dataset was used to reconstruct global temperature, as featured in the IPCC’s Sixth Assessment Report. For the past 2000 years, we collaborated with colleagues internationally through the Past Global Changes (PAGES) program to generate global multi-proxy data sets of paleotemperature, and to reconstruct temperatures for each continent, and the Arctic.

Both temperature and hydroclimate data have been compiled for the Arctic and for western North America. These were used to reconstruct climate changes in Alaska and Yukon, Canada and Greenland, and the North Atlantic and Scandinavia during the Holocene, as well as hydroclimate of North America over the past 2000 years.

In Utah, we collaborated with the US Geological Survey in a broad-ranging investigation of the paleoenvironments of Bear Lake and its catchment.

Opportunities

Students Wanted

I am seeking graduate (MS and PhD levels) and undergraduate students to join my research group. I have current and pending funding for research projects in Alaska and elsewhere.

Financial support: All students who are accepted to the graduate program are funded as either Teaching or Research Assistants. Undergraduate assistants are frequently needed for the lab and the field.

Graduate degrees: My students pursue their Master’s degree in either Geology or in the Paleoenvironments Emphasis of Environmental Sciences & Policy, and their PhD degree in Earth Sciences & Environmental Sustainability with an emphasis in either Climate & Environmental Change or Earth Systems.

For more information: Please contact me or any of my graduate students for information about the graduate programs at Northern Arizona University. NAU has a great deal to offer students, and Flagstaff is a wonderful town in an attractive, high-elevation, American West setting.

Career paths: Since 1995, I have served as the primary advisor for 36 successful graduate students. Almost all of the MS theses have led to publications in scientific journals. My students have gone on to professional careers in: geoscience consultants, government- and university-based scientists, university professors, college instructors, and small business owners.

Facilities: Students are trained in both field and laboratory procedures. The laboratory combines techniques in sediment analyses and geochronology, including radiocarbon. Daily operations are overseen by a full-time laboratory manager.

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Kevin preparing samples for biogenic Si analysis

Field equipment: lake coring platform, percussion corer, Uwitec surface corer, automated sediment traps, logging sensors for hydrological and meteorological parameters, conductivity-temperature-depth loggers, recording sonar

Sediment lab equipment: particle size analyzer, hyperspectral core scanner, magnetic susceptibility, onsite cold room, microscopes, microbalance, sonicators, drying ovens

Sediment lab procedures: radiocarbon sample preparation, ABA treatment, diatom purification, cryptotephra separation, biogenic silica content, loss on ignition

Amino acid geochronology lab equipment: high performance liquid chromatographs, high precision ovens, laminar flow hood

People

My students and I work closely with others in the Past and Present Climate Change research area in the School of Earth & Sustainability, including professors Nick McKay, Scott Anderson, Cody Routson and Michael Erb. We collaborate with the Center for Ecosystem Science and Society, and with many specialists in the US and internationally.

Darrell Kaufman
Darrell is a Regents’ Professor in the School of Earth and Sustainability. He has been researching the Quaternary geology and paleoclimatology of Alaska for over 30 years. He has a special interest in geochronology and in coordinating large collaborative science synthesis projects.

Brief CV
Google Scholar

Current Graduate Students

Leah Marshall
Leah is PhD student in Earth Sciences & Environmental Sustainability. She is researching carbon accumulation in Alaskan permafrost. After receiving her BS in Geology and Environmental Science from William & Mary (2019), Leah worked through AmeriCorps at a National Historical Park in Vermont.

Hunter Allen
Hunter is a PhD student in Earth Science & Environmental Sustainability. He is researching proglacial lakes in Alaska, using rockflour as a proxy for glacial change in the Holocene. He received his MS in Geoscience from the University of Massachusetts Amherst (2023) and his BS in Environmental Science at Sierra Nevada University (2021).

Aryaana Khan
Aryaana is a PhD student in Earth Science & Environmental Sustainability. She is researching amino acids and radiocarbon in lake sediments to reconstruct past climates. She received her MA in Environmental Sustainability & Decision Making with a focus on Environmental Science from St. John’s University (2024), and her BS in Biology from the City College of New York (2022).

Laboratory Manager

Jordon Bright
Jordon received his PhD in Geosciences (University of Arizona) in 2017. He oversees the operation of the Quaternary geochronology and the sediments laboratories. His research expertise includes using ostracodes assemblages and geochemistry to reconstruct Quaternary paleoenvironmental changes in western North America.

Completed Graduate Students and Postdoctoral Researchers (with their current positions)

Maurycy Żarczyński, 2023-2024, Visiting researcher, Polish National Agency for Academic Exchange Bekker Programme. Last glacial-interglacial environmental at Stoneman Lake, AZ using novel hyperspectral imaging techniques (Professor, Oceanography & Geography, University of Gdanask, Poland)

Laura Larocca, 2022-2023, NOAA Climate and Global Change Postdoctoral Fellow. Circum-Arctic glacier snowline altitudes over the last four decades (Professor, School of Ocean Futures, Arizona State University)

Scarlett Hunt, 2023, MS Geology, Amino acid racemization in Quaternary foraminifra from the Southern Ocean (School teacher, Flagstaff)

Caitlin Walker, 2023, Environmental Sciences – Paleoenvironments, Holocene eolian sediment and organic matter from terraces and hillslopes around Healy, central Alaska

Joshua Smith, 2022, MS Geology, Amino acid geochronology of foraminifera from the central Arctic Ocean and Nordic Seas

Ellie Broadman, 2021, PhD Earth Sciences & Environmental Sustainability, Holocene hydroclimate in southern and Arctic Alaska inferred from diatom oxygen isotopes and data-model comparisons (Biologist, Sequoia & Kings Canyon Field Station, US Geological Survey)

Emmy Wroblenski, 2021, MS Environmental Sciences – Paleoenvironments, Multi-proxy evidence for climatic and environmental change during the Late Glacial and Holocene at Kelly Lake, Kenai Peninsula, Alaska (Environmental Scientist, Mott MacDonald, Seattle)

Annie Wong, 2019, MS Environmental Sciences – Paleoenvironments, Timing and rate of Skilak River outwash plain aggradation based on evidence from Pothole Lake, south-central Alaska.

Rebecca Ellerbroek, 2018, MS Geology, Three-component hydrograph separation for the glaciated Lake Peters catchment, Arctic Alaska (Instructor, Northern Arizona University)

Christopher (Chris) Benson, 2018, MS Geology, 16,000 years of paleoenvironmental change from the Lake Peters- Schrader area, northeastern Brooks Range, Alaska (Hydrologic Technician, US Geological Survey, Utah Water Science Center, Moab, UT)

Douglas Steen, 2016, MS Geology, Late Quaternary paleomagnetism and environmental magnetism at Cascade and Shainin Lakes, north-central Brooks Range, Alaska (Data Integration Analyst, COE Distributing)

Paul Zander, 2015, MS Geology, Tephrochronology and paleoenvironmental change during the past 15,000 years at Whitshed Lakes, south-central Alaska (PostDoc, Max Planck Institute for Chemistry)

Jonathan Griffith, 2014, MS Geology, A multi-proxy record of Holocene paleoenvironmental and paleoclimate change at Lake Token, south-central Alaska (Education and Outreach Associate, University Colorado, Boulder)

Taylor LaBrecque, 2014, MS Geology, Holocene glacier fluctuations inferred from proglacial-lacustrine sediment cores from Emerald Lake, Kachemak Bay, Alaska (Environmental consulting, Maine)

Brandon Boldt, 2013, MS Quaternary Sciences, A multi-proxy approach to reconstructing Holocene climate variability at Kurupa River valley, Arctic Alaska (Brewmeister, Denver, CO)

Anne Krawiec (Hamblin), 2013, MS Geology, Holocene tephrochronology and storminess inferred from two lakes on Adak Island, Alaska (Professional Development Coordinator,, Northern Arizona University)

David Vaillencourt, 2013, MS Quaternary Sciences, Five-thousand years of hydroclimate variability on Adak Island, Alaska inferred from dD of n-alkanoic acids (Orion GMP Solutions, Organic chemistry, Colorado Springs, CO)

Chris Kassel, 2009, MS Geology, Lacustrine evidence from Mother Goose Lake of Holocene geothermal activity at Mount Chiginagak, Alaska Peninsula (Geologist, Arcadis Consultancy, Syracuse, NY)

Heidi Roop, 2009, MS Geology, Climate influence on varve sedimentation at Cascade Lake, Ahklun Mountains, southwestern Alaska (Professor, University of Minnesota)

Caleb Schiff, 2007, MS Geology, Late Holocene storm-trajectory changes inferred from the oxygen isotope composition of lake diatoms (Restaurant owner, Pizzicletta, Flagstaff, AZ)

Nicholas McKay, 2007, MS Geology, Late Holocene climate at Hallet and Greyling Lakes, central Chugach Range, south-central Alaska (Professor, Northern Arizona University)

Thomas Daigle, 2006, MS Geology, Late Holocene climate change at Goat Lake, Kenai Mountains, south-central Alaska (Consulting Geologist, Denver, CO)

Kasey Kathan, 2006, MS Geology, Late Holocene climate fluctuations at cascade Lake, northeastern Ahklun Mountains, southwestern Alaska (Vermont Dept of Environmental Conservation)

Janelle Sikorski, 2004, MS Geology, Little Ice Age glacier fluctuations and winter precipitation, Brooks Range, Alaska (Instructor, University Alaska, Anchorage, AK)

Christian deFontaine, 2004, MS Geology, Holocene tephrochronology, Cook Inlet, Alaska (Environmental Scientist, U.S. Geological Survey)

Nicholas Balascio, 2003, MS Geology, Late Wisconsin equilibrium-line altitudes, Brooks Range, Alaska (Professor, Earth & Climate Sciences, Bates College, Lewiston, Maine)

Jordon Bright, MS Quaternary Sciences, 2003, Oxygen isotopes and ostracodes in a 250,000-year-long core from, Bear Lake, Utah/Idaho (Research Associate, Northern Arizona University)

Laura Levy, MS Geology, 2002, Late Holocene glacier fluctuations, Ahklun Mountains, SW Alaska (Professor, Humbolt State University, CA)

Gary O’Brien, MS Geology, 2002, Oxygen isotope composition of banded Quaternary travertine, Grand Canyon National Park, Arizona (Research Associate, Utah State University, Logan, UT)

Benjamin Laabs, MS Geology, 2001, Quaternary lake-level and tectonic geomorphology, Bear Lake Valley, Utah/Idaho (Professor, North Dakota State University, Fargo)

Yarrow Axford, MS Geology, 2000, Late Quaternary glacier fluctuations and vegetation change in the northwestern Ahklun Mountains, SW Alaska (Professor, Northwestern University, IL)

Kathy Lemke, MS Geology, 2000, Holocene tephrochronology of the Homer area, Cook Inlet, Alaska (Lecturer, Puget Sound Community College, WA)

Jason Briner, MS Geology, 1999, Late Wisconsin glacial chronology of the western Ahklun Mountains, SW Alaska (Professor, University of Buffalo, New York)

Jeffrey Bigelow, MS Geology, 1998, Amino acid geochronology of the Lahontan basin, Nevada (Waterborne Environmental, Saratoga Springs, NY)

David Bouchard, MS Geology, 1997, Quaternary Bear River paleohydrogeography reconstructed from the 87Sr/86Sr composition of lacustrine fossils

Amy Hochberg, MS Geology, 1996, Aminostratigraphy of Thatcher Basin, SE Idaho–Reassessment of Pleistocene lakes (Geology Instructor, Utah State University)

Caleb Thompson, MS Geology, 1996, Pre-late Wisconsin glacial history of the Naknek River valley, SW Alaska (Database developer, MongoDB, New York)

Karen Stilwell (Miller), MS Geology, 1995, Late Quaternary glacial geology, shoreline morphology, and tephrochronology of the Iliamna/Naknek/Brooks Lake area, SW Alaska (President, M2 Resource Consulting)