Quantitative palaeotemperature records inferred from fossil pollen and chironomid assemblages from Lake Gilltjärnen, northern central Sweden

Abstract

AbstractPalaeotemperature reconstructions based on radiocarbon‐dated fossil pollen and chironomid stratigraphies obtained from Lake Gilltjärnen 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. yr BP 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 Gilltjärnen and its catchment. Comparison of the present results with a lake‐level reconstruction from Lake Ljustjärnen, ca. 100 km southwest of Lake Gilltjärnen, shows that the low early‐Holocene temperatures were associated with high lake‐levels at 10 500–8500 cal. yr BP, 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. Copyright © 2006 John Wiley & Sons, Ltd.