Seasonal temperatures for the past ～400 years reconstructed from diatom and chironomid assemblages in a high-altitude lake (Lej da la Tscheppa,Switzerland) |
| |
| Authors: | Lucien von Gunten Oliver Heiri Christian Bigler Jacqueline van Leeuwen Carlo Casty André F Lotter Michael Sturm |
| |
| Institution: | 1.Institute of Geography,University of Bern,Bern,Switzerland;2.Palaeoecology, Institute of Environmental Biology, Laboratory of Palaeobotany and Palynology,Utrecht University,Utrecht,The Netherlands;3.NCCR Climate,University of Bern,Bern,Switzerland;4.Ecology and Environmental Science,Ume? University,Umea,Sweden;5.Institute of Plant Sciences,University of Bern,Bern,Switzerland;6.Climate and Environmental Physics,University of Bern,Bern,Switzerland;7.Department of Surface Waters (SURF),Swiss Federal Institute for Environmental Science and Technology (EAWAG),Dubendorf,Switzerland |
| |
| Abstract: | We analysed a 42 cm long sediment record from Lej da la Tscheppa, a high-altitude lake (2,616 m a.s.l.) in the Upper Engadine
valley (Switzerland) for subfossil diatoms, chironomids and pollen. The chronology of the top 21 cm 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. 400 years, 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. |
| |
| Keywords: | Alpine lake Diatoms Chironomids Pollen Ice-cover Seasonal temperature reconstructions |
| 本文献已被 SpringerLink 等数据库收录！ |
|
