Continental European Eemian and early Wurmian climate evolution: comparing signals using different quantitative reconstruction approaches based on pollen
Résumé
Analyses of Eemian climate dynamics based on different reconstruction methods were conducted for several pollen sequences in the northern alpine foreland. The modem analogue and mutual climate sphere techniques used, which are briefly presented, complement one another with respect to comparable results. The reconstructions reveal the occurrence of at least two similar thermal periods, representing temperate oceanic conditions warmer and with a higher humidity than today., Intense changes of climate processes become obvious with a shift of winter temperatures of about 15degreesC from the late Rissian to the first thermal optimum of the Eemian. The transition shows a pattern of summer temperatures and precipitation increasing, more rapidly than winter temperatures. With the first optimum during the Pinus-Quercetum mixtum-Corylus phase (PQC) at an early stage of the Eemian and a second optimum period at a later stage, which is characterised by widespread Carpinus, climate gradients across the study area were less intense than today. Average winter temperatures vary between -1.9 and 0.4degreesC (present-day -3.6 to 1.4degreesC), summer temperatures between 17.8 and. 19.6degreesC, (present-day 14 to 18.9degreesC). The timberline expanded about 350 m when compared to the present-day limit represented by Pinus mugo. Whereas the maximum of temperature parameters is related to the first optimum, precipitation above 1100 mm is higher during the second warm period concomitant to somewhat reduced temperatures. Intermediate, smaller climate oscillations and a cooling becomes obvious, which admittedly represent moderate deterioration but not extreme chills. During the boreal semicontinental Eemian Pinus-Picea-Abies phase, another less distinct fluctuation occurs, initiating the oscillating shift from temperate to cold conditions. (C) 2003 Elsevier Science B.V All rights reserved.