HIGH-RESOLUTION HOLOCENE TEMPERATURE VARIABILITY AND BIOGEOCHEMICAL RECONSTRUCTIONS FROM LAMINATED LAKE SEDIMENTS OF SOUTHWESTERN GREENLAND

Instrumental records demonstrate that temperature in southwestern Greenland shows strong negative correlation with the North Atlantic Oscillation (NAO). Thus, high-resolution records of temperature from southwestern Greenland can contribute to a more robust reconstruction and help reveal spatial variations of the NAO throughout the North Atlantic region during the Holocene. We have previously reported unusually high concentrations of long-chain alkenones (LCAs) in sediments from a suite of laminated lakes in the Sondre Stromfjord region of southwestern Greenland (67^oN, 51^oW). Decadal-scale alkenone unsaturation (UK37) records from three of these lakes depict remarkable coherence, providing unique records of regional temperature variability for the mid- to late Holocene. Comparison of these records with other highly-resolved temperature reconstructions from the North Atlantic suggests millennial-scale oscillations in the dominant mode of NAO over the past ~6000 yrs. Records of sedimentary LCA concentration from the lakes also imply regional control over the productivity of prymnesiophyte algae. While total organic carbon (TOC) records can yield clues to the overall productivity of a lake basin, LCAs are purely aquatic in origin and therefore represent ideal biomarkers for autochthonous productivity and facilitate refined paleolimnologic and paleoclimatic interpretation. Sediment traps were deployed in the saline lakes in April 2006, collecting discrete seston samples during spring and summer at 10 day intervals. We are presently using water temperature data collected over the same time interval (which included the spring thaw) to create an absolute UK37 temperature calibration specific to the Greenland lakes. Ongoing work on the saline lakes of the Sondre Stromfjord region also involves compound-specific δD analysis and algal culturing. Up-to-date results will be presented in the meeting.