Late Glacial and Holocene temperature changes at Egelsee,Switzerland, reconstructed using subfossil chironomids |
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Authors: | Isabelle Larocque-Tobler Oliver Heiri Michael Wehrli |
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Institution: | 1.Institut National de Recherche Scientifique (INRS), Centre Eau, Terre et Environnement,Quebec,Canada;2.Palaeoecology, Institute of Environmental Biology, Faculty of Science,Utrecht University,Utrecht,The Netherlands;3.Institut für Pflanzenwissenschaften,Universit?t Bern,Bern,Switzerland;4.Oeschger Centre for Climate Change Research and Institute of Geography,University of Bern,Bern,Switzerland |
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Abstract: | A temperature reconstruction using chironomids was attempted at Egelsee, Switzerland, a site where pollen and macrofossil
records showed a correspondence between vegetation and climatic changes inferred by other proxies in Europe. The general pattern
of temperature changes inferred from chironomids during the Late Glacial i.e. cold temperatures between ca. 16,500 and 14,800 cal
BP, close to present-day temperature between 15,000 and 13,000 cal BP and colder temperatures during the Younger Dryas (YD)],
and the major temperature changes of the Holocene (i.e. the Younger Dryas–Holocene transition and the Late Holocene cooling
trend) at Egelsee, were mirrored in other European climate reconstructions using various proxies. However, the amplitude of
temperature changes during the YD was smaller than reconstructed by other proxies at various sites, and the 8,200 years BP
event was not apparent. These differences between records were probably due to the dominance of Corynocera ambigua, with percentages reaching 60% in parts of the Egelsee sequence. This taxon was not present in any of the 103 lakes used
for the transfer function and its absence may have yielded less accurate inferences. Its presence in samples only associated
with cold inferences at Egelsee suggests that this taxon is a cold indicator. However, it was also found in warm Danish lakes
and the factors that determine the presence of C. ambigua remain unexplained. Most samples had a poor fit to temperature and instead, dissolved organic carbon seemed to be a factor
influencing the chironomid assemblages during the Holocene. These results illustrate the need to better understand the ecology
of chironomids and to disentangle the various factors that affect chironomid communities through time. Ultimately, such information
will lead to more accurate temperature reconstructions. |
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