NOAA/WDS Paleoclimatology - Baffin Island Lakes Surface Sediment Leaf Wax Hydrogen Isotope Data

The hydrogen isotope composition of plant waxes preserved in lacustrine sediments is a potentially valuable tool for reconstructing paleoenvironmental changes in the Arctic. However, in contrast to the mid- and low-latitudes, significantly less effort has been directed towards understanding the factors controlling D/H fractionation in high latitude plant waxes and the impact of these processes on the interpretation of sedimentary leaf wax dD records. To better understand these processes, we examined the D/H ratios of long chain fatty acids in lake surface sediments spanning a temperature and precipitation gradient on Baffin Island in the eastern Canadian Arctic. D/H ratios of plant waxes increase with increasing temperature and aridity, with values ranging from -240 per mil to -160 per mil over the study area. Apparent fractionation factors between n-alkanoic acids in Arctic lake sediments and precipitation (EFA-ppt) are less negative than those of mid-latitude lakes and modern plants by 25 per mil to 65 per mil, consistent with n-alkane data from modern Arctic plants (Yang et al., 2011). Furthermore, EFA-ppt values from Arctic lakes become systematically more positive with increasing evaporation, in contrast to mid-latitude sites, which show little to no change in fractionation with aridity. These data are consistent with enhanced water loss and isotope fractionation at higher latitude in the Arctic summer, when continuous sunlight supports increased daily photosynthesis. The dominant control on dDFA variations on Baffin Island is temperature. However, changing EFA-ppt result in steeper dDFA-temperature relationships than observed for modern precipitation. The application of this dDFA-based paleotemperature calibration to existing dDFA records from Baffin Island produces much more realistic changes in late Holocene temperature and highlights the importance of these effects in influencing the interpretation of Arctic dDFA records. A better understanding of the controls on hydrogen isotope fractionation in high latitude leaf waxes will be essential to the proper interpretation of isotope records from sedimentary plant waxes in the Arctic.