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Seasonal temperatures for the past ∼400years reconstructed from diatom and chironomid assemblages in a high-altitude lake (Lej da la Tscheppa, Switzerland)

von Gunten, Lucien ; Heiri, Oliver ; Bigler, Christian ; van Leeuwen, Jacqueline ; Casty, Carlo ; Lotter, André ; Sturm, Michael

In: Journal of Paleolimnology, 2008, vol. 39, no. 3, p. 283-299

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    Titre
    • Seasonal temperatures for the past ∼400years reconstructed from diatom and chironomid assemblages in a high-altitude lake (Lej da la Tscheppa, Switzerland)
    Auteur
    • von Gunten, Lucien. Institute of Geography, University of Bern, Hallerstrasse 12, 3012, Bern, Switzerland
    • Heiri, Oliver. Palaeoecology, Institute of Environmental Biology, Laboratory of Palaeobotany and Palynology, Utrecht University, Budapestlaan 4, 3584 CD, Utrecht, The Netherlands
    • Bigler, Christian. NCCR Climate, University of Bern, 3012, Bern, Switzerland
    • van Leeuwen, Jacqueline. Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013, Bern, Switzerland
    • Casty, Carlo. Climate and Environmental Physics, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
    • Lotter, André. Palaeoecology, Institute of Environmental Biology, Laboratory of Palaeobotany and Palynology, Utrecht University, Budapestlaan 4, 3584 CD, Utrecht, The Netherlands
    • Sturm, Michael. Department of Surface Waters (SURF), Swiss Federal Institute for Environmental Science and Technology (EAWAG), 8600, Dubendorf, Switzerland
    Type de document
    • Postprint
    Langue
    • Anglais
    Publié dans
    • Journal of Paleolimnology, 2008, vol. 39, no. 3, p. 283-299. Springer Netherlands
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:309884
    Summary
    We analysed a 42cm long sediment record from Lej da la Tscheppa, a high-altitude lake (2,616ma.s.l.) in the Upper Engadine valley (Switzerland) for subfossil diatoms, chironomids and pollen. The chronology of the top 21cm of the record was established using 210Pb analysis using a constant-rate-of-supply model, and validated with 137Cs measurements and the content of spheroidal carbonaceous particles. A tentative chronology for the lower part of the core was obtained through extrapolation of the sedimentation rates in the uppermost part of the record. Pollen assemblages in the record reflect regional changes in forestation and land-use patterns in the Upper Engadine valley and show no evidence of significant local human activity in the lake's catchment. Diatom assemblages record a distinct increase in planktonic taxa since the early 19th century, suggesting a decrease in the duration of ice-cover. In contrast, chironomid assemblages remained stable during a large part of the record. We applied an established chironomid-based July air temperature transfer function and a newly developed diatom-based spring air temperature transfer function to reconstruct past seasonal air temperature changes at Lej da la Tscheppa. The reconstructions indicate a diatom-inferred warming trend in spring temperatures during the past ca. 400years, whereas chironomid-inferred summer temperatures suggest a slight cooling trend. These biota-based reconstructions are in good agreement with the centennial-scale temperature trend in an independent reconstruction of regional temperatures in the Upper Engadine region based on instrumental records and documentary proxy evidence from the Alps. Our results suggest that, in high-altitude lakes, independent chironomid- and diatom-based seasonal temperature reconstruction is possible and can be successfully used to track seasonal temperature trends