Peter E. Sauer
Biogeochemistry and Paleoclimatology
- Ph.D., 1997, University of Colorado at Boulder
- B.A., 1988, Carleton College
My research makes use of geochemical proxies to reconstruct the paleoclimatic history of the earth. Through climate reconstructions, it is my goal to improve our understanding of climatic variability, both in terms of the sensitivity of the climate system to various forcings and the range of variability expressed, and both as a result of natural forcing variability and anthropogenic causes. I focus on isotopic tracers of paleoclimate, but the interpretation of stable isotope records depends on an understanding of a variety of other proxy data, including fossil pollen, geomorphic evidence, marine micropaleontology and chemical stratigraphy, and historical records. My research focuses on the following questions.
What chemical fractions of sediments can be used as a proxy for lakewater isotopic composition? In the past few years, new technology (developed in large part by former IU Geology Prof. John Hayes and his students) has enabled us to make unprecedented measurements of hydrogen isotope ratios (D/H) on individual organic compounds. This approach offers several advantages over commonly used methods. Paleolimnologists interested in reconstructing lakewater isotopic composition have generally been restricted to 18O/16O ratios of calcium carbonate of aquatic fossils and sediment cellulose, both of which can be subject to severe limitations. The oxygen isotopic composition of carbonate is affected by temperature-dependent fractionation effects, and sediment cellulose can contain significant amounts derived from terrestrial sources, which affects its isotopic composition. For the past few years, I have been pursuing the possibility of using D/H ratios of certain biomarker lipids as a means of overcoming both of these problems.
How well can stable isotope ratios in freshwater systems be used as a proxy for climate conditions? Whereas stable isotope ratios of oxygen (18O/16O) and hydrogen (D/H) in precipitation are well correlated with mean annual temperature in most cold parts of the world, this signal is not always directly mapped into the isotopic composition of lakewater. For example, evaporation, both in the lake and in the watershed, can be important because it preferentially removes light isotopes, leaving the remaining water enriched in the heavy isotope. In general, these factors can be evaluated only through a rigorous program of hydrologic monitoring. I headed an isotopic monitoring program of lakewater near Iqaluit (Nunavut, Arctic Canada) to examine these effects.
How do lake-sediment based records of climate contribute to regional paleoclimate histories, and what does that tell us about climate sensitivity? Many environmental variables must be considered together to define climate. Because different climate proxies are sensitive to different variables, a wide range of paleoclimate proxies must be studied in order to generate the most reliable climate reconstructions. Depending on the hydrologic condition of the lakes, isotopes may reflect mean annual temperatures or the may also contain a significant evaporation signal. In order to make sense of lake-sediment based records, one must interpret them in light of other evidence from other proxies that are sensitive to temperature and water balance. Regional and global paleoclimate syntheses nearly always conclude that climate change is spatially heterogeneous. By comparing my paleoclimate records from one part of the world with records from other parts of globe, it is possible to determine the timing and geographical extent of anomalies, which can then help lead to an understanding of the forcing that caused the anomaly. The ultimate goal of this research is to relate the forcing to the size of the anomaly, thereby gaining a better understanding of how the climate system works.
Are hydrogen isotope ratios in terrestrial leaf-wax components a viable proxy for humidity? Humidity is a climate variable that is difficult to reconstruct. However, it may be that D/H ratios of leaf-wax components (n-alkanes, long-chain fatty acids, and long-chain n-alkanols) can be used as a proxy for evaporation. Plant physiologists have determined that water within the leaves of vascular plants becomes isotopically enriched due to evaporation. The degree of isotopic enrichment increases as humidity decreases. If leafwater isotopic enrichment is recorded in the leaf wax components as preliminary data suggest, then it may be possible to use the D/H of leaf wax components in sedimentary systems as an integrated, basin-wide paleo-humidity proxy. If successful, this means of obtaining paleo-humidity information would have important ramifications for paleobotanical and paleoclimate studies. These projects illustrate the kind of study which can be undertaken now using new geochemical approaches. The overarching theme I wish to address in my future research is, What is the climate history of the earth? What caused these changes, and what can we predict about future environmental change based on the paleoenvironmental record?
I occasionally teach G104 (Earth System History) and G117 (Environmental Geology).
Górka, M., P.E. Sauer, D. Lewicka–Szczebak, and M.–O. Jedrysek (2011) Carbon isotope signature of dissolved inorganic carbon (DIC) in precipitation and atmospheric CO2. Environmental Pollution 159, 294–301. (doi:10.1016/j.envpol.2010.08.027) http://dx.doi.org/10.1016/j.envpol.2010.08.027
Gröcke, D. R., van Hardenbroek, M., Sauer, P., and Elias, S., 2011. Hydrogen Isotopes in Beetle Chitin. In: Gupta, S. N. (Ed.), Chitin: formation and diagenesis. Springer.
Lis, G. P. and Sauer, P. E., 2010. Ranges of hydrogen isotope ratios in natural materials. In: Beauchemin, D. and Matthews, D. E. (Ed.), The Encyclopedia of Mass Spectrometry, Vol. 5. Elsevier.
Sauer, P. E., 2010. Use of stable isotopes to study climate. In: Beauchemin, D., and Matthews, D. E. (Ed.),The Encyclopedia of Mass Spectrometry, Vol. 5. Elsevier.
Sauer, P. E. and Lis, G. P., 2010. Ranges of oxygen isotopes in natural materials. In: Beauchemin, D., and Matthews, D. E. (Ed.), The Encyclopedia of Mass Spectrometry, Vol. 5. Elsevier.
Schimmelmann, A. and Sauer, P. E., 2010. Methods to prepare water as H2 for IRMS measurement of 2H. In: Matthews, D. E. (Ed.), The Encyclopedia of Mass Spectrometry. Elsevier.
Sauer, P.E., A. Schimmelmann, A.L. Sessions, and K. Topalov (2009) Simplified batch equilibration for D/H determination of non-exchangeable hydrogen in solid organic material. Rapid Communications in Mass Spectrometry 23 (7), 949–956. http://dx.doi.org/10.1002/rcm.3954
Schimmelmann, A., M. Mastalerz, L. Gao, P.E. Sauer, and K. Topalov (2009) Dike intrusions into bituminous coal, Illinois Basin: H, C, N, O isotopic responses to rapid and brief heating. Geochimica et Cosmochimica Acta 73, 6264–6281. http://dx.doi.org/10.1016/j.gca.2009.07.027
Schimmelmann, A., A. Albertino, P.E. Sauer, H. Qi, R. Molinie, and F. Mesnard (2009) Nicotine, acetanilide and urea multi-level 2H–, 13C– and 15N–abundance reference materials for continuous–flow isotope ratio mass spectrometry. Rapid Communications in Mass Spectrometry 23, 3513–3521. http://dx.doi.org/10.1002/rcm.4277
Henning, M., D. Strąpoć, G. Lis, P. Sauer, J. Fong, A. Schimmelmann, and L.M. Pratt (2007) Versatile inlet system for on-line compound-specific δD and δ13C GC-ox/red–IRMS analysis of gaseous mixtures. Rapid Communications in Mass Spectrometry 21, 2269–2272. http://dx.doi.org/10.1002/rcm.3083
Miller, G. H., Wolfe, A. P., Briner, J. P., Sauer, P. E., and Nesje, A., 2005. Holocene glaciation and climate evoluation of Baffin Island, Arctic Canada. Quaternary Science Reviews 24, 1703–1721. http://dx.doi.org/10.1016/j.quascirev.2004.06.021
Miller, G.H., Wolfe, A.P., Steig, E., Sauer, P.E., Kaplan, M.R., and Briner, J.P., 2002. The Goldilocks dilemma: Big ice, little ice, or "just right" ice in the eastern Canadian Arctic: Quaternary Science Reviews 21, 33–48. http://dx.doi.org/10.1016/S0277-3791(01)00085-3
Sauer, P.E., T.I. Eglinton, J.M. Hayes, A. Schimmelmann, and A. Sessions (2001) Compound–specific D/H ratios of lipid biomarkers from sediments as a proxy for environmental and climatic conditions. Geochimica et Cosmochimica Acta 65, 213–222. http://dx.doi.org/0.1016/S0016-7037(00)00520-2
Sauer, P.E., Miller, G.H., and Overpeck, J.T., (2001) Oxygen isotope ratios of organic matter in arctic lakes as a paleoclimate proxy: field evidence and laboratory investigations: Journal of Paleolimnology, v. 25, p. 43–64. http://dx.doi.org/10.1023/A:1008133523139
Miller, G. H., Mode, W. N., Wolfe, A. P., Sauer, P. E., Bennike, O., Forman, S. L., Short, S. K., Stafford, T. W., Jr., and Williams, K. M., 1999. Stratified interglacial lacustrine sediments from Baffin Island, Arctic Canada: Chronology and paleoenvironment and implications. Quaternary Science Reviews 18, 789–810. http://dx.doi.org/10.1016/S0277-3791(98)00075-4
Sauer, P. E. and Sternberg, L. d. S. L. O., 1994. Improved method for the determination of oxygen isotopic composition of cellulose. Analytical Chemistry 66, 2409–2411. http://dx.doi.org/10.1021/ac00086a030
At the department level, I am a member of the Undergraduate Committee. At the university level, I am the director of a new undergraduate degree program, the B.S. in Environmental Science; this is a truly interdisciplinary science degree that has been developed over the past 5 years and now available for the Bloomington campus. At the state level, I have regularly participated in numerous out-reach and science education programs for K-12 education. On the national level, I am a regular reviewer for national journals and for NSF.