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Quantitative multiproxy assessment of long-term patterns of Holocene environmental change from a small lake near Abisko, northern SwedenClimate Impacts Research Centre, Abisko Scientific Research Station, SE-981 07 Abisko, and Umeå University, Department of Ecology and Environmental Science, SE-901 87 Umeå, Sweden; Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland christian.bigler{at}ips.unibe.ch
Climate Impacts Research Centre, Abisko Scientific Research Station, SE-981 07 Abisko, and Umeå University, Department of Ecology and Environmental Science, SE-901 87 Umeå, Sweden; IGBP/PAGES, Bärenplatz 2, CH-3011 Bern, Switzerland
Botanical Institute, University of Bergen, Allégaten 41, NO-5007 Bergen, Norway
Botanical Institute, University of Bergen, Allégaten 41, NO-5007 Bergen, Norway; Environmental Change Research Centre, University College London, 26 Bedford Way, London WCIH OAP, UK
Climate Impacts Research Centre, Abisko Scientific Research Station, SE-981 07 Abisko, and Umeå University, Department of Ecology and Environmental Science, SE-901 87 Umeå, Sweden; Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L 3G1 Quantitative reconstructions are made of Holocene changes in climatic and environmental conditions from analyses of pollen, chironomids and diatoms in identical stratigraphic levels of a sediment core from Vuoskkujávri (68°20'43 N, 19°06'00 E, 348 m a.s.l.) near Abisko in northern Sweden (Lapland). Transfer functions, based on regional calibration sets, are applied to reconstruct Holocene patterns in mean July air temperature (using all three indicators), mean January air temperature (pollen), annual precipitation (pollen) and lakewater pH (diatoms). During periods with ‘good’ fit to the modern calibration sets all mean July air-temperature inferences based on the three proxy indicators reveal a general trend of decreasing temperature: pollen-inferred mean July air temperature shows a decrease of c. 1.1°C since 7500 cal. yrs BP; the chironomids show a decrease of c. 1.2°C since the early Holocene; whereas the diatoms show a decrease of c. 1.5°C since 6000 cal. yrs BP. Pollen-inferred mean January air temperature indicates that winters may have been warmer by c. 3.0°C during the early Holocene, followed by a gradual cooling until 8500 cal. yrs BP (c. 1.0°C warmer than today) and a subsequent warming until 7000 cal. yrs BP (c. 2.0°C warmer than today). Since 7000 cal. yrs BP, a gradual cooling towards the present-day values is inferred. According to the pollen, annual precipitation may have been considerably higher during the early Holocene than today (c. +150 mm) and increased until 7000 cal. yrs BP (c. +320 mm). Since 7000 cal. yrs BP, annual precipitation decreased continuously towards present-day values. Diatom-inferred pH trends show that natural acidification of c. 0.5 pH units followed deglaciation; present-day values were reached c. 5000 cal. yrs BP. The early Holocene is identified as a problematic time period for the application of modern calibration sets, as diatoms show ‘poor’ fit to the calibration set from 10 600 to 6000 cal. yrs BP, pollen from 10 600 to 7500 cal. yrs BP, and chironomids from 10 250 to 10 000 cal. yrs BP. Compared with estimates from the COHMAP GCM model, mean July air-temperature inferences based on biological proxies at Vuoskkujávri suggest a more moderate decrease in temperature over the past 9000 years.
Key Words: Pollen • chironomids • diatoms • Subarctic • Lapland • precipitation • pH • temperature • multiproxy approach • quantitative inferences • weighted averaging partial least squares (WA-PLS) • Holocene
The Holocene, Vol. 12, No. 4,
481-496 (2002) This article has been cited by other articles:
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