Late Holocene humidity variability in central Sweden
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
The aim of this thesis was to reconstruct humidity variability in central Sweden during the late Holocene. A multi-proxy approach was used to infer humidity changes as recorded in a lake and a mire. Age-models were constructed based on radiocarbon dating and the Askja-1875 tephra. Stable isotopes (δ18O and δ13C) on Chara spp encrustations and Pisidium spp mollusc shells and carbon content were analysed in the lake record, whereas peat stratigraphy, humification, testate amoebae assemblages, C/N ratio and stable isotopes (δ13C and δ15N) were analysed in the mire record. Stable isotopes (δ2H and δ18O) on lake water showed that Lake Blektjärnen responded to changes in the balance between evaporation and input water (E/I ratio). A high E/I ratio results from a dry and probably warmer climate during which evaporation and atmospheric equilibration likely enrich lake water in 18O and 13C, respectively, and vice versa for a low E/I ratio. The relatively high Chara δ18O and δ13C values between ca 4400 and 4000 cal yr BP thus suggest relatively dry and likely warm conditions, whereas depleted values suggest wetter and probably cooler conditions between ca 4000 and 3000 cal yr BP. Again, drier and probably warmer conditions were inferred from the relatively enriched δ18O values between ca 2500 and 1000 cal yr BP, and depleted δ18O values were recorded between ca 1000 and 50 cal yr BP indicating wetter and likely cooler conditions. The results from the mire mainly indicated vegetation succession, however, the changes inferred at ca 2600 and 1000 cal yr BP could have been triggered by climate change. This study shows that the proxies responded sensitively to humidity changes in the investigated archives allowing for reconstruction of climate change in central Sweden during late Holocene.
Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography and Quaternary Geology, Stockholm University , 2010. , 60 p.
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 20
humidity change, stable isotopes, Chara spp, Pisidium spp, testate amoebae assemblages, humification, C/N ratio, late Holocene, central Sweden
Research subject Quarternary Geology
IdentifiersURN: urn:nbn:se:su:diva-36884ISBN: 978-91-7155-929-6OAI: oai:DiVA.org:su-36884DiVA: diva2:290897
2010-03-05, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
Chambers, Frank, professor
Wastegård, Stefan, professorRosqvist, Gunhild, professorSchoning, Kristian, doktor
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Submitted. Paper 3: Accepted. Paper 5: In progress.2010-02-112010-01-282010-10-07Bibliographically approved
List of papers