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Quantitative palaeotemperature records inferred from fossil pollen and chironomid assemblages from Lake Gilltjärnen, northern central Sweden
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
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2006 (English)In: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 21, no 8, 831-841 p.Article in journal (Refereed) Published
Abstract [en]

Palaeotemperature reconstructions based on radiocarbon-dated fossil pollen and chironomid stratigraphies obtained from Lake Gilltjarnen provide evidence of climate changes during the last 11 000 years in the boreal zone of northern central Sweden. The records show consistent trends during the early and mid-Holocene, indicating low temperatures at 11 000-10 000 cal. yr BP, followed by a rising trend and a period of maximum values from about 7000 to 4000 cal. yr BP. At 3000 cal. yrBP the chironomid-inferred temperature values rise abruptly, deviating from the late-Holocene cooling trend indicated by the pollen-based reconstruction and most of the other palaeotemperature records from central Scandinavia, probably as a result of local limnological changes in Lake Gilltjarnen and its catchment. Comparison of the present results with a lake-level reconstruction from Lake Ljustjarnen, ca. 100 km southwest of Lake Gilitjarnen, shows that the low early-Holocene temperatures were associated with high lake-levels at 10500-8500 cal. yrBP, whereas low lake-levels and dry conditions prevailed during the period of high temperatures at between 7500 and 5000 cal. yr BP, probably due to high summer evapotranspiration and lower precipitation.

Place, publisher, year, edition, pages
2006. Vol. 21, no 8, 831-841 p.
Keyword [en]
sediments, pollen, chironomids, Holocene thermal maximum, dryness
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:uu:diva-94348DOI: 10.1002/jqs.1004ISI: 000242681800003OAI: oai:DiVA.org:uu-94348DiVA: diva2:168170
Available from: 2006-04-13 Created: 2006-04-13 Last updated: 2011-05-04Bibliographically approved
In thesis
1. Holocene Climate in Central and Southern Sweden: Quantitative Reconstructions from Fossil Data
Open this publication in new window or tab >>Holocene Climate in Central and Southern Sweden: Quantitative Reconstructions from Fossil Data
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In quantitative palaeoecology modern species-environmental relationships can be statistically modelled, and recent development has made the calibration models more statistically robust. These models are used to transform fossil assemblages to quantitative estimates of past environmental conditions. The aim of this thesis is to infer Holocene temperatures from fossil pollen data sampled from lakes in central and southern Sweden. This reconstruction is done by using a north-European pollen-climate calibration model, which was extended with 37 modern pollen samples from the southern deciduous vegetation zone in Sweden within this project. A statistical method is used for deriving the pollen-climate calibration model, weighted averaging partial least square (WA-PLS) method. The long term trends in pollen inferred temperatures from this study reflect low, but rapidly rising temperatures in the early-Holocene, a trend that was temporarily interrupted by a cool period about 8500 cal yr BP, but continued after 8000 cal yr BP. A Holocene thermal maximum (HTM) with temperatures roughly 2°C higher than at present was recorded about 7000 cal yr BP and by 4000 cal yr BP pollen inferred temperatures starts to decline. In order to create a more comprehensive picture of past climate patterns in the investigated area inferred temperatures from this study are compared with independent palaeorecords, a stable oxygen isotope record for moisture variability (paper I) and chironomids for summer temperature (paper II). Taken all together, these records reflect a coherent Holocene climate pattern which also is supported by several studies from Scandinavia and the north Atlantic region. Pollen inferred temperatures and the moisture record are indicating markedly dry, continental climate conditions in southern Sweden during the HTM possibly as a result of reorganisations in regional atmosphere circulations. The local observations in this study of regional climate events, such as the cold period at about 8200 cal yr BP and the dry period at about 7000 to 4000 cal yr BP are of particular interest because they suggest that vegetation in the study region has responded sensitively both to long-term climatic trends and more transient climate events.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 37 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 168
Quaternary geology, pollen analysis, climate reconstructions, transfer functions, vegetation dynamics, Sweden, Kvartärgeologi
urn:nbn:se:uu:diva-6805 (URN)91-554-6539-0 (ISBN)
Public defence
2006-05-08, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00
Available from: 2006-04-13 Created: 2006-04-13 Last updated: 2013-05-23Bibliographically approved

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