LACUSTRINE BIOMARKER RECONSTRUCTION OF ARCTIC CLIMATE BEFORE, DURING, AND AFTER THE MID-PLIOCENE WARM PERIOD

The mid-Pliocene warm period (~3.26 to 3.025 Ma) was the last time that atmospheric greenhouse gasses were as high as today, and so serves as an essential guide to understanding Earth’s future equilibrium climate and climate variability. To this end, numerous modeling efforts and climate reconstructions have been carried out to evaluate Pliocene temperatures and they suggest global warming of 2-3 °C relative to the pre-industrial period. There are little data available, however, on mid-Pliocene warming in the Arctic, which is expected to be substantially greater than low-latitude warming. Here we present a combination of published and unpublished Arctic paleoclimate data spanning from 3.4 to 2.4 Ma (including the M2 cooling at 3.3 Ma) based on biomarkers preserved in the sedimentary record of Lake El’gygytgyn, Siberia. Glycerol dialkyl glycerol tetraethers (GDGTs) were analyzed at ~2000-year spacing over the 1 million year interval and branched GDGTs (bGDGT) were used to estimate absolute temperatures and temperature variability. We further discuss the presence and distributions of isoprenoid GDGTs and hydroxyl-GDGTs in the context of bGDGT temperature variability, orbital-scale climate forcings, and late Pliocene glacial excursions.