QUANTITATIVE PALEOTEMPERATURE ESTIMATES FROM d18O IN CHIRONOMID HEAD CAPSULES FROM ARCTIC LAKE SEDIMENT

General Circulation Model (GCM) simulations of future greenhouse warming show the Arctic is likely to experience the greatest warming, a prediction supported by observed temperature increases over the past century, thinning of arctic sea ice in recent decades, and negative glacier mass balances. The predicted polar amplification of global warming can be tested by comparing quantitative records that assess the magnitude and rate of arctic climate variability with similar records from other regions. Sediments from arctic lakes provide widespread paleoenvironmental records with decadal-scale resolution, but reconstructions have been hampered by the relative insensitivity of many traditional environmental proxies. Here we show that the d¹⁸O values in head capsules of chironomid (midge) larvae are equilibrated with the d¹⁸O of the lakewater in which they live. In suitable lakes, lakewater d¹⁸O is controlled by the d¹⁸O of catchment precipitation, which is strongly correlated to mean annual temperature. From these correlations, chironomid d¹⁸O can be used to provide quantitative estimates of past changes in mean annual air temperature (plus and minus 1 °C). We compare our Holocene temperature reconstructions based on chironomid d¹⁸O with temperature reconstructions derived from chironomid faunal assemblages. We demonstrate the potential of chironomid d¹⁸O for paleotemperature reconstructions in an arctic lake, which could resolve a long-standing discrepancy for the onset of Holocene warmth in Greenland.