We present results from multiple stable isotope analyses (δ18O of chironomid larval head capsules, chironomid adult thoraxes and other insect remains and δD, δ13C, δ15N of total organic matter-TOM) of a lake sediment core (04-SVID-03) taken from Stora Vidarvatn in northeastern Iceland to reconstruct past environmental, limnological and δ18O of past lake water changes during the Holocene. Core 04-SVID-03 represents a ∼12,000 cal. yrs BP to present record. Large magnitude changes in δ18O occurred during the Holocene at the site. Downcore shifts in δ18O of chironomids did not correlate with measurements of the δ13C and δ15N of chironomid head capsules, implying that the δ18O changes were not primarily driven by changes in chironomid diet during the Holocene. The δD of TOM provided a proxy of relative lake-water δD changes at the site and also showed large magnitude changes during the record. This approach was supported by analyses of a modern training set where δDTOM analyses were conducted using surface sediments from a suite of freshwater lakes over a large latitudinal gradient. The magnitude of changes in both the δ18O and δD and the relatively negative δ18O values throughout much of the core suggest that the proxies represent more paleoenvironmental information than solely temperature. Additional possible influences on lake-water isotopic composition are discussed, including changes in the seasonality of precipitation, in the patterns of air masses supplying precipitation to Iceland and in the dominant mode of the North Atlantic Oscillation.
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Acknowledgements We thank our Icelandic colleagues and collaborators for their support during our field work, including Áslaug Geirsdóttir. We thank Gifford Miller for discussions related to this research. Funding for the research presented in this paper came from a US National Science Foundation grant awarded to Wooller (NSF-EAR-0317766). Field work was supported by NSF-EAR-0317766, NSF ATM-0318479 to G. Miller, RANNIS (Icelandic Centre for Research) Grant 060236021 to Á. Geirsdóttir, and VECO Polar Resources. G. Gunnarsdottir and family provided access to the field site and generous hospitality. We thank Diane O’Brien (UAF) for allowing us to use the microscope in her laboratory to take images of insect remains from our samples. We also thank Thora Hrafnsdottir from the Natural History Museum of Kopavogur, Iceland for identifying some of the remains from our core. Peter Sauer collected the water samples from Baffin Island. We also thank the Icelandic coring perfectionists Thorsteinn Jónsson and Sveinbjorn Steinthorsson for their energy and ideas for coring lake sediments. We thank two anonymous reviewers for their constructive suggestions, which improved our paper.
Copyright 2008 Elsevier B.V., All rights reserved.
- Stable isotopes
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