A sedimentary record from lake Stora Vioarvatn in northeast Iceland records environmental changes over the past 2000 years. Downcore data include chironomid (Diptera: Chironomidae) assemblage data and total organic carbon, nitrogen, and biogenic silica content. Sample scores from detrended correspondence analysis (DCA) of chironomid assemblage data are well correlated with measured temperatures at Stykkishólmur over the 170 year instrumental record, indicating that chironomid assemblages at Stora Vioarvatn have responded sensitively to past temperature changes. DCA scores appear to be useful for quantitatively inferring past temperatures at this site. In contrast, a quantitative chironomid-temperature transfer function developed for northwestern Iceland does a relatively poor job of reconstructing temperature shifts, possibly due to the lake's large size and depth relative to the calibration sites or to the limited resolution of the subfossil taxonomy. The pre-instrumental climate history inferred from chironomids and other paleolimnological proxies is supported by prior inferences from historical documents, glacier reconstructions, and paleoceanographic studies. Much of the first millennium AD was relatively warm, with temperatures comparable to warm decades of the twentieth century. Temperatures during parts of the tenth and eleventh centuries AD may have been comparably warm. Biogenic silica concentrations declined, carbon:nitrogen ratios increased, and some chironomid taxa disappeared from the lake between the thirteenth and nineteenth centuries, recording the decline of temperatures into the Little Ice Age, increasing soil erosion, and declining lake productivity. All the proxy reconstructions indicate that the most severe Little Ice Age conditions occurred during the eighteenth and nineteenth centuries, a period historically associated with maximum sea-ice and glacier extent around Iceland.
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Acknowledgements A. Haag, Þ. Jónsson, E. McNie, H. Rosner, K. B. Ólafsdóttir, S. Ólafsdóttir, and S. Steinþórsson helped in the field. Warm thanks to G. Gunnarsdóttir and family for their hospitality and repeated access to the study site. Discussions with T. Hrafnsdóttir and C. Kuzawa, and feedback from N. Holmes, D. Kaufman, and two anonymous reviewers improved this paper greatly. A. Bini, O. Darko, and E. Thomas assisted with chironomid sample preparation. S. Ólafsdóttir and K. B. Ólafsdóttir measured organic carbon content at the University of Iceland Institute of Earth Sciences. D. Kaufman and C. Schiff at Northern Arizona University provided BSi analyses. C:N and C isotopes were measured at the University of California at Davis Stable Isotope Laboratory. The University of Colorado Radiocarbon Laboratory prepared 14C samples. 210Pb analyses were conducted at MyCore Scientific, Inc. H. Jiang shared paleoceanographic data. This research was supported by the Comer Science and Education Foundation, the National Science Foundation (ARC-0455025 and DGE-9987607), RANNIS (Icelandic Centre for Research, grant 0402330121-3), the Science Institute of the University of Iceland, VECO Polar Resources, and the Geological Society of America. This work is a contribution to the NSF-ARCSS collaborative project, ‘‘A synthesis of the last 2000 years of climatic variability from Arctic lakes.’’
Copyright 2009 Elsevier B.V., All rights reserved.
- Holocene paleoclimate
- Little Ice Age