Aaron Diefendorf

Aaron Diefendorf


Professor, Organic and Isotope Geochemistry

Geology-Physics Building


A&S Geology - 0013

Professional Summary

My research uses stable isotope and organic biogeochemical tools to solve critical questions in the areas of global climate change, carbon cycling, Earth’s climate sensitivity, paleoclimatology, and paleoecology.


Ph.D.: Pennsylvania State University 2010 (Geosciences and Biogeochemistry)

M.S.: University of Saskatchewan Canada, 2005 (Geological Sciences)

B.S.: University of Tennessee 2002 (Honors Geology)

B.F.A.: University of Tennessee 2002 (Studio Art Ceramics)

Research and Practice Interests

Earth’s climate is warming at a pace and magnitude unprecedented in recent times, with profound consequences for terrestrial ecology and hydrology. My research aims to contribute to our understanding of future global change by examining Cenozoic changes in climate, ecology, and the carbon cycle. Fossil chemical signatures—biomarkers—and their carbon isotope ratios integrate and track the ancient carbon cycle and provide unique paleoecological information in sediments where other proxies are not often preserved. The combination of biomarkers and carbon isotopes provides new insights into the feedbacks between global change, terrestrial ecology, and the carbon cycle.

Please see my website for current information, a curriculum vitae, information about our organic and isotope geochemistry facilities.

Positions and Work Experience

2011 -2017 Assistant Professor, University of Cincinnati,

2017 -2021 Associate Professor, University of Cincinnati,

2021 - Professor, University of Cincinnati,

Research Support

Grant: #60163-ND2 Investigators:Diefendorf, Aaron 07-01-2019 -08-31-2021 American Chemical Society - National Chapter Developing Diatom Biomarkers and Their C and H Isotopic Compositions for Oil-Rock Source Correlation Role:PI $110,000.00 Active Level:Private Non-Profit

Grant: #EAR-1636546 Investigators:Diefendorf, Aaron 09-01-2016 -08-31-2018 National Science Foundation Evaluating plant carbon isotope fractionation as a pCO2 proxy for the geologic record Role:PI $138,189.00 Active Level:Federal

Grant: #EAR-1636740 Investigators:Diefendorf, Aaron; Lowell, Thomas 08-01-2016 -07-31-2018 National Science Foundation Collaborative Research: Identifying basin-specific controls on isotopic and chronological offsets of lake sediment leaf wax hydrogen isotope records Role:PI $222,636 Active

Grant: #OSGC Student-Innovative-Creative-Hands-on Project (SICHOP) grant Investigators:Czaja, Andrew; Diefendorf, Aaron; Hamilton, Trinity; Havig, Jeff 06-06-2016 -12-31-2016 National Aeronautics and Space Administration Midwest Geobiology Conference Role:Collaborator $2,000.00 Awarded Level:Federal

Grant: #KIGMR 2016-2017 Investigators:Diefendorf, Aaron 06-01-2016 -04-30-2017 Korea Institute of Ocean Science and Technology Hydrologic conditions in western North America during the Last Interglacial Role:PI $31,284.71 Active Level:Foreign Institution of Higher Education

Grant: #AI 010348-002 Investigators:Diefendorf, Aaron; Havig, Jeff 06-01-2016 -05-31-2017 Agouron Institute Agouron Small Grant in Aid conference funds for 10/15/16 event (Grant No.AI-SGIA-203.16.1) Role:Collaborator $8,000.00 Awarded Level:Private Non-Profit

Grant: #KIGMR 2015-2016 Investigators:Diefendorf, Aaron 07-01-2015 -04-30-2016 Korea Institute of Geoscience and Mineral Resources North Hemisphere mid-latitude paleovegetation response to moisture changes during the late Quaternary Role:PI $29,000.00 Awarded Level:Foreign Non-Profit

Grant: #EAR-1229114 Investigators:Diefendorf 09-15-2012 -08-31-2015 NSF MRI: Acquisition of Stable Isotope Instrumentation for Biogeochemistry Research and Teaching at the University of Cincinnati Role:PI $400,000 ($571,428 total) Active Type:Grant Level:National

Grant: #OBR AF Investigators:Diefendorf 09-15-2012 -08-31-2015 Ohio Board of Regents Action Fund In support of NSF Grant. Role:PI $85,714 Active Type:Grant

Grant: #PRF# 5187-DN12 Investigators:Diefendorf, Aaron 01-01-2012 -08-31-2016 American Chemical Society - National Chapter Terrestrial Biomarker Transport Mechanisms and Implications for Interpreting Terrestrial Signals in Oils and Bitumens Role:PI $100,000.00 Active Level:Private Non-Profit

Grant: #EAR-2039795 Investigators:Diefendorf, Aaron; Lowell, Thomas 08-01-2021 -07-31-2024 National Science Foundation Collaborative Proposal: Tapping an unused biomarker for insights of past evaporation Role:PI 367265.00 Awarded Level:Federal

Grant: #EAR-2110297 Investigators:Crowley, Brooke; Diefendorf, Aaron 09-01-2021 -08-31-2022 National Science Foundation Acquisition of a high temperature elemental analyzer for hydrogen and oxygen isotope analysis of waters and solids for the University of Cincinnati Stable Isotope Laboratory Role:PI 108503.00 Awarded Level:Federal

Grant: #CSU 200001700 Investigators:Diefendorf, Aaron 04-15-2022 -04-14-2023 Department of Agriculture Biogeochemical consequences of updating an aging agricultural infrastructure (backdoor) Role:PI 24695.00 Awarded Level:Federal


Peer Reviewed Publications

Suh, Y. J.; Diefendorf, A. F.; Freimuth, E. J.; Hyun, S. (2020. ) Last interglacial (MIS 5e) and Holocene paleohydrology and paleovegetation of midcontinental North America from Gulf of Mexico sediments .Quaternary Science Reviews, , 227 ,

Schlanser, K.; Diefendorf, A. F.; Greenwood, D. R.; Mueller, K. E.; West, C. K.; Lowe, A. J.; Basinger, J. F.; Currano, E. D.; Flynn, A. G.; Fricke, H. C.; Geng, J.; Meyer, H. W.; Peppe, D. J. (2020. ) On geologic timescales, plant carbon isotope fractionation responds to precipitation similarly to modern plants and has a small negative correlation with pCO2 .Geochimica et Cosmochimica Acta, , 270 ,264-281

Freimuth, E. J.; Diefendorf, A. F.; Lowell, T. V.; Bates, B. R.; Schartman, A.; Bird, B. W.; Landis, J. D.; Stewart, A. K. (2020. ) Contrasting sensitivity of lake sediment n-alkanoic acids and n-alkanes to basin-scale vegetation and regional-scale precipitation δ2H in the Adirondack Mountains, NY (USA) .Geochimica et Cosmochimica Acta, , 268 ,22-41

Wise, J. L.; Van Horn, D. J.; Diefendorf, A. F.; Regier, P. J.; Lowell, T. V.; Dahm, C. N. (2019. ) Dissolved organic matter dynamics in storm water runoff in a dryland urban region .Journal of Arid Environments, , 165 ,55-63

Suh, Y. J.; Diefendorf, A. F.; Bowen, G. J.; Cotton, J. M.; Ju, S. J. (2019. ) Plant wax integration and transport from the Mississippi River Basin to the Gulf of Mexico inferred from GIS-enabled isoscapes and mixing models .Geochimica et Cosmochimica Acta, , 257 ,131-149

Freimuth, E. J.; Diefendorf, A. F.; Lowell, T. V.; Wiles, G. C. (2019. ) Sedimentary n-alkanes and n-alkanoic acids in a temperate bog are biased toward woody plants .Organic Geochemistry, , 128 ,94-107

Diefendorf, A. F.; Leslie, A. B.; Wing, S. L. (2019. ) A phylogenetic analysis of conifer diterpenoids and their carbon isotopes for chemotaxonomic applications .Organic Geochemistry, , 127 ,50-58

Bird, M. I.; Brand, M.; Diefendorf, A. F.; Haig, J. L.; Hutley, L. B.; Levchenko, V.; Ridd, P. V.; Rowe, C.; Whinney, J.; Wurster, C. M.; Zwart, C. (2019. ) Identifying the â??savannaâ?? signature in lacustrine sediments in northern Australia .Quaternary Science Reviews, , 203 ,233-247

Vrazo, M. B.; Diefendorf, A. F.; Crowley, B. E.; Czaja, A. D. (2018. ) Late Cretaceous marine arthropods relied on terrestrial organic matter as a food source: Geochemical evidence from the Coon Creek Lagerstätte in the Mississippi Embayment .Geobiology, , 16 (2 ) ,160-178

Suh, Y. J.; Diefendorf, A. F. (2018. ) Seasonal and canopy height variation in n-alkanes and their carbon isotopes in a temperate forest .Organic Geochemistry, , 116 (2 ) ,23-34

Arnold, T. E.; Diefendorf, A. F.; Brenner, M.; Freeman, K. H.; Baczynski, A. A. (2018. ) Climate response of the Florida Peninsula to Heinrich events in the North Atlantic .Quaternary Science Reviews, , 194 (2 ) ,1-11

Freimuth, E. J.; Diefendorf, A. F.; Lowell, T. V. (2017. ) Hydrogen isotopes of n-alkanes and n-alkanoic acids as tracers of precipitation in a temperate forest and implications for paleorecords .Geochimica et Cosmochimica Acta, , 206 (2 ) ,166-183

Diefendorf, A. F.; Freimuth, E. J. (2017. ) Extracting the most from terrestrial plant-derived n-alkyl lipids and their carbon isotopes from the sedimentary record: A review .Organic Geochemistry, , 103 (2 ) ,1-21

Date, P.; Crowley-Gall, A.; Diefendorf, A. F.; Rollmann, S. M. (2017. ) Population differences in host plant preference and the importance of yeast and plant substrate to volatile composition .Ecology and Evolution, , 7 (11 ) ,3815-3825

Kallenbach, C. M.; Grandy, A. S.; Frey, S. D.; Diefendorf, A. F. (2015. ) Microbial physiology and necromass regulate agricultural soil carbon accumulation .Soil Biology and Biochemistry, , 91 (11 ) ,279-290

Giri, S. J.; Diefendorf, A. F.; Lowell, T. V. (2015. ) Origin and sedimentary fate of plant-derived terpenoids in a small river catchment and implications for terpenoids as quantitative paleovegetation proxies .Organic Geochemistry, , 82 (11 ) ,22-32

Diefendorf, A. F.; Sberna, D. T.; Taylor, D. W. (2015. ) Effect of thermal maturation on plant-derived terpenoids and leaf wax n-alkyl components .Organic Geochemistry, , 89-90 (11 ) ,61-70

Diefendorf, A. F.; Leslie, A. B.; Wing, S. L. (2015. ) Leaf wax composition and carbon isotopes vary among major conifer groups .Geochimica et Cosmochimica Acta, , 170 (11 ) ,145-156

Diefendorf, A. F.; Freeman, K. H.; Wing, S. L.; Currano, E. D.; Mueller, K. E. (2015. ) Paleogene plants fractionated carbon isotopes similar to modern plants .Earth and Planetary Science Letters, , 429 (11 ) ,33-44

Marin-Spiotta, E.; Chaopricha, N. T.; Plante, A. F.; Diefendorf, A. F.; Mueller, C. W.; Grandy, A. S.; Mason, J. A. (2014. ) Long-term stabilization of deep soil carbon by fire and burial during early Holocene climate change .Nature Geoscience, , 7 (6 ) ,428-432

Diefendorf, A. F.; Freeman, K. H.; Wing, S. L. (2014. ) A comparison of terpenoid and leaf fossil vegetation proxies in Paleocene and Eocene Bighorn Basin sediments .Organic Geochemistry, , 71 (6 ) ,30-42

Clyde, W. C.; Gingerich, P. D.; Wing, S. L.; Röhl, U.; Westerhold, T.; Bowen, G.; Johnson, K.; Baczynski, A. A.; Diefendorf, A.; McInerney, F.; Schnurrenberger, D.; Noren, A.; Brady, K.; Acks, R.; Baczynski, A.; Belcher, C.; Bowen, G.; Brady, K.; Clyde, W.; Collinson, M.; D'Ambrosia, A.; Denis, E.; Freeman, K.; Gingerich, P.; Harrington, G.; Jardine, P.; Johnson, K.; Kraus, M.; Maibauer, B.; Noren, A.; Riedel, J.; Röhl, U.; Schnurrenberger, D.; Schouten, S.; Tsukui, K.; Weijers, J.; Welter, G.; Westerhold, T.; Wing, S.; Wittkopp, F.; Wood, A. (2013. ) Bighorn Basin Coring Project (BBCP): A continental perspective on early Paleogene hyperthermals .Scientific Drilling, , 71 (16 ) ,21-31

Close, H. G.; Shah, S. R.; Ingalls, A. E.; Diefendorf, A. F.; Brodie, E. L.; Hansman, R. L.; Freeman, K. H.; Aluwihare, L. I.; Pearson, A. (2013. ) Export of submicron particulate organic matter to mesopelagic depth in an oligotrophic gyre .Proceedings of the National Academy of Sciences of the United States of America, , 110 (31 ) ,12565-12570

Diefendorf, A. F.; Freeman, K. H.; Wing, S. L. (2012. ) Distribution and carbon isotope patterns of diterpenoids and triterpenoids in modern temperate C 3 trees and their geochemical significance .Geochimica et Cosmochimica Acta, , 85 (31 ) ,342-356

Cui, Y.; Kump, L. R.; Ridgwell, A. J.; Charles, A. J.; Junium, C. K.; Diefendorf, A. F.; Freeman, K. H.; Urban, N. M.; Harding, I. C. (2012. ) Reply to 'Constraints on hyperthermals' .Nature Geoscience, , 5 (4 ) ,231-232

Freeman, K. H.; Mueller, K. E.; Diefendorf, A. F.; Wing, S. L.; Koch, P. L. (2011. ) Clarifying the influence of water availability and plant types on carbon isotope discrimination by C3 plants .Proceedings of the National Academy of Sciences of the United States of America, , 108 (16 ) ,E59-E60

Diefendorf, A. F.; Freeman, K. H.; Wing, S. L.; Graham, H. V. (2011. ) Production of n-alkyl lipids in living plants and implications for the geologic past .Geochimica et Cosmochimica Acta, , 75 (23 ) ,7472-7485

Cui, Y.; Kump, L. R.; Ridgwell, A. J.; Charles, A. J.; Junium, C. K.; Diefendorf, A. F.; Freeman, K. H.; Urban, N. M.; Harding, I. C. (2011. ) Slow release of fossil carbon during the palaeocene-eocene thermal maximum .Nature Geoscience, , 4 (7 ) ,481-485

Mueller, K. E.; Diefendorf, A. F.; Freeman, K. H.; Eissenstat, D. M. (2010. ) Appraising the roles of nutrient availability, global change, and functional traits during the angiosperm rise to dominance .Ecology Letters, , 13 (5 ) ,E1-E6

Diefendorf, A. F.; Mueller, K. E.; Wing, S. L.; Koch, P. L.; Freeman, K. H. (2010. ) Global patterns in leaf 13C discrimination and implications for studies of past and future climate .Proceedings of the National Academy of Sciences of the United States of America, , 107 (13 ) ,5738-5743

Cui, Y.; Kump, L. R.; Ridgwell, A.; Diefendorf, A.; Junium, C. K. (2010. ) A high-resolution record from Svalbard of carbon release during the Paleocene-Eocene thermal maximum .Journal of Earth Science, , 21 (SUPPL. 1 ) ,190

Schouten, S.; Hopmans, E. C.; Van Der Meer, J.; Mets, A.; Bard, E.; Bianchi, T. S.; Diefendorf, A.; Escala, M.; Freeman, K. H.; Furukawa, Y.; Huguet, C.; Ingalls, A.; Ménot-Combes, G.; Nederbragt, A. J.; Oba, M.; Pearson, A.; Pearson, E. J.; Rosell-Melé, A.; Schaeffer, P.; Shah, S. R.; Shanahan, T. M.; Smith, R. W.; Smittenberg, R.; Talbot, H. M.; Uchida, M.; Van Mooy, B. A. S.; Yamamoto, M.; Zhang, Z.; Damsté, J. S. S. (2009. ) An interlaboratory study of TEX86 and BIT analysis using high-performance liquid chromatography-mass spectrometry .Geochemistry, Geophysics, Geosystems, , 10 (3 ) ,190

Diefendorf, A. F.; Patterson, W. P.; Holmden, C.; Mullins, H. T. (2008. ) Carbon isotopes of marl and lake sediment organic matter reflect terrestrial landscape change during the late Glacial and early Holocene (16,800 to 5,540 cal yr B.P.): A multiproxy study of lacustrine sediments at Lough Inchiquin, western Ireland .Journal of Paleolimnology, , 39 (1 ) ,101-115

Tibert, N. E.; Patterson, W. P.; Diefendorf, A. F.; Martini, A.; Stanton, C. (2007. ) Holocene temperature variability in western Ireland: Evidence from limnic ostracode assemblages and stable isotope values .Stratigraphy, , 4 (4 ) ,353-361

Diefendorf, A. F.; Patterson, W. P.; Mullins, H. T.; Tibert, N.; Martini, A. (2006. ) Evidence for high-frequency late Glacial to mid-Holocene (16,800 to 5500 cal yr B.P.) climate variability from oxygen isotope values of Lough Inchiquin, Ireland .Quaternary Research, , 65 (1 ) ,78-86

Diefendorf, A. F.; Patterson, W. P. (2005. ) Survey of stable isotope values in Irish surface waters .Journal of Paleolimnology, , 34 (2 ) ,257-269

Professional Affiliation

Geological Society of America,

American Geophysical Union,

Sigma Xi,

American Association for the Advancement of Science,

Courses Taught

-GEOL-1014 GEOL THRU FILM Level:Undergraduate

THE EARTH SYSTEM Level:Undergraduate

Organic Geochemistry Level:Both

Stable Isotope Biogeochemistry Level:Both

Geoscience Workshop: Techniques in Stable Isotopes Level:Graduate