HIGH-LATITUDE ENVIRONMENTAL CHANGE DURING MIS 8 - 12: BIOGEOCHEMICAL EVIDENCE FROM LAKE EL'GYGYTGYN NE RUSSIA

Marine Isotope Stages (MIS) 11 has been proposed as an analog for the present interglacial; however, terrestrial records of this time period are rare. Sediments from Lake El’gygytgyn (67°30’N, 172°5’E) in North East Russia contain a 3.56 Ma record of climate variability from the Arctic. Organic geochemical analyses can provide insight into the climatic and environmental response during this critical period. Here, we present an organic geochemical reconstruction of environmental and climatic changes from MIS 8 through 12. Terrestrial vegetation changes, as revealed by n-alkane indices (CPI, TAR) and concentrations of arborinol (a biomarker for trees), show increased tree cover around the lake during interglacial periods, with higher concentrations observed during MIS 11 as compared to MIS 9. A similar pattern is also observed in records of aquatic productivity revealed by molecular indicators from dinoflagellates (dinosterol), eustigmatophyte algae (long-chain (C₂₈-C₃₂) 1,15 n-alkyl diols) in addition to short-chain n-alkanes, as aquatic productivity is highest during the MIS 11 interglacial period. Additionally, changes recorded in these molecular proxies reflect relative temperature variability as recorded by the MBT/CBT paleothermometer, based on branched glycerol dialkyl glycerol tetraethers (GDGTs), which corresponds with pollen record and diatom δ¹⁸O temperature estimates of ~ 9 - 12 degrees C of variability, compiled by other studies. These records of environmental and climatic change indicate Arctic sensitivity to external forcings such as orbital variability and atmospheric greenhouse gas concentrations. Overall, this study indicates that organic geochemical analyses of the Lake El’gygytgyn sediment archive reveals the sensitivity and strong response of the lake and surrounding ecosystems to glacial-interglacial climate change.