Lake-level records and palaeoclimates of northern Eurasia

Sammanfattning: This thesis documented lake-level changes across Eurasia and made reconstructions of regional climates and atmospheric circulation patterns during the late Quaternary; analysed temporal signals in lake record; used lake data to improve pollen-based quantitative recostructions of climate; and compared lake data with simulated P-E fields from Atmospheric General Circulation (AGC) models. Lake records from northern Eurasia showed regionally-coherent patterns during the late Quaternary, in response to changes in insolation and glaciation (Papers I and II appended in the thesis). Time series analysis of European lake status through the Holocene (Paper III) has led to the identification of seven distinct patterns of lake behaviour, each characteristic of a specific geographical region. Three periods (9, 7 and 4ka B.P.) of rapid changes were corresponded to times when the atmospheric circulation regime underwent a rapid reorganization. Constrained-analogue reconstructions using pollen and lake data (Paper IV) esitmated quantitatively annual precipitation, runoff (P-E), mean temperature of the coldest month, mean temperature of the warmest month, and growing degree days above 5C at 6000 yr B.P., and showed strong regional and seasonal patterns across Europe. Predicted 6ka P-E fields from 5 AGC models have provided a mechanistic explanation for changes in lake status, e.g. insolation-induced enhancement of Asian monsoon (Paper V). The simulated mean annual conditions in Mediterranean region is consistent with lake data, but seasonality of changes is not consistent with pollen data. Some suggestion for improvement of the simulations was provided in the paper.