Paleohygrometry and reconstruction of lake evaporation history based on compound-specific hydrogen and oxygen isotope analyses of biomarkers – principle of the coupled isotope approach, advances and limitations

<p>The oxygen and hydrogen isotopic composition &#948;²H and &#948;¹⁸O of leaf and lake water reflects the isotopic composition of source water/precipitation modified by evapo(transpi)rative enrichment. This later enrichment can be illustrated and quantified using &#948;²H- &#948;¹⁸O diagrams and the deuterium-excess. The enrichment of leaf water thereby depends primarily on relative air humidity (RH) and can be investigated using biomarkers being produced in leaves. The enrichment of lake water depends on lake evaporation and can be investigated using biomarkers being produced by aquatic macrophytes or algae. Provided that unambiguous terrestrial and aquatic biomarkers can be identified in lake sediments, the coupling of &#948;²H and &#948;¹⁸O hence allows reconstructing RH (paleohygrometry approach) and lake evaporation history. In our contribution, we discuss the potential, the advances and the limitation of the coupled isotope approach based on leaf wax-derived <em>n</em>-alkane and hemicellulose-derived sugar biomarkers (&#948;²H<em>_n</em>_-alkanes- &#160;&#948;¹⁸O_sugars).</p> <p>&#160;</p> <p>References</p> <p>Hepp, J., Mayr, C., Rozanski, K., Sch&#228;fer, I., Tuthorn, M., Glaser, B., Juchelka, D., Stichler, W., Zech, R. and Zech, M., 2021. Validation of a coupled &#948;²H<em>_n</em>_-alkane-&#948;¹⁸O_sugar paleohygrometer approach based on a climate chamber experiment. Biogeosciences 18, 5363-5380.</p> <p>Hepp, J., W&#252;thrich, L., Bromm, T., Bliedtner, M., Sch&#228;fer, I. K., Glaser, B., Rozanski, K., Sirocko, F., Zech, R., and Zech, M., 2019. How dry was the Younger Dryas? Evidence from a coupled &#948;²H-&#948;¹⁸O biomarker paleohygrometer applied to the Lake Gem&#252;ndener Maar sediments, Western Eifel, Germany, Climate of the Past 15, 713-733.</p> <p>Zech, M., Tuthorn, M., Detsch, F., Rozanski, K., Zech, R., Z&#246;ller, L., Zech, W. and Glaser, B., 2013. A 220 ka terrestrial &#948;¹⁸O and deuterium excess biomarker record from an eolian permafrost paleosol sequence, NE-Siberia. Chemical Geology 360-361, 220-230.</p>