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Clim. Past Discuss., 3, 165-195, 2007
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Spatial structure of the 8200 cal yr BP event in Northern Europe

H. Seppä1, H. J. B. Birks2,3,4, T. Giesecke5, D. Hammarlund6, T. Alenius7, K. Antonsson8, A. E. Bjune2,3, M. Heikkilä1, G. M. MacDonald9, A. E. K. Ojala7, R. J. Telford2,3, and S. Veski10
1Department of Geology, P.O. Box 64, 00014, University of Helsinki, Finland
2Department of Biology, University of Bergen, Allégaten 55, 5007 Bergen, Norway
3Bjerknes Centre for Climate Research, Allégaten 55, 5007, Bergen, Norway
4Environmental Change Research Centre, University College London, 26 Bedford Way, London, WC1H OAP, UK
5Department of Geography, University of Liverpool, Roxby Building, Liverpool, L69 7ZT, UK
6GeoBiosphere Science Centre, Quaternary Sciences, Lund University, Sölvegatan 12, 223 62 Lund, Sweden
7Geological Survey of Finland, P.O. Box 96, 02151, Espoo, Finland
8Department of Earth Sciences, Uppsala University, Villavägen 16, 75236, Uppsala, Sweden
9Department of Geography, UCLA, 405 Hilgard Avenue, Los Angeles, CA 90095-1524, USA
10Institute of Geology, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia

Abstract. A synthesis of well-dated high-resolution pollen records suggests a spatial structure in the 8200 cal yr BP event in northern Europe. The temperate, thermophilous tree taxa, especially Corylus, Ulmus, and Alnus, decline abruptly between 8300 and 8000 cal yr BP at most sites located south of 61° N, whereas there is no clear change in pollen values at the sites located in the North-European tree-line region. Pollen-based quantitative temperature reconstructions and several other, independent palaeoclimate proxies, such as lacustrine oxygen-isotope records, reflect the same pattern, with no detectable cooling in the sub-arctic region. The observed pattern would challenge the general view of the wide-spread occurrence of the 8200 cal yr BP event in the North Atlantic region. An alternative explanation is that the cooling during the 8200 cal yr BP event took place mostly during the winter and spring, and the ecosystems in the south responded sensitively to the cooling during the onset of the growing season. In contrast, in the sub-arctic area, where the vegetation was still dormant and lakes ice-covered, the cold event is not reflected in pollen-based or lake-sediment-based records. The arctic regions may therefore not always be optimal for detecting past climate changes.

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Citation: Seppä, H., Birks, H. J. B., Giesecke, T., Hammarlund, D., Alenius, T., Antonsson, K., Bjune, A. E., Heikkilä, M., MacDonald, G. M., Ojala, A. E. K., Telford, R. J., and Veski, S.: Spatial structure of the 8200 cal yr BP event in Northern Europe, Clim. Past Discuss., 3, 165-195, 2007.   Bibtex   EndNote   Reference Manager