Seasonal variability of Holocene climate a palaeo

Authors: Ricarda Voigt Eberhard Grüger Janina Baier Dieter Meischner

Publish Date: 2008/05/14

Volume: 40, Issue: 4, Pages: 1021-1052

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Abstract

Studies combining sedimentological and biological evidence to reconstruct Holocene climate beyond the major changes and especially seasonality are rare in Europe and are nearly completely absent in Germany The present study tries to reconstruct changes of seasonality from evidence of annual algal successions within the framework of wellestablished pollen zonation and 14CAMS dates from terrestrial plants Laminated Holocene sediments in Lake Jues 10°207′ E 51°393′ N 241 m asl located at the SW margin of the Harz Mountains central Germany were studied for sediment characteristics pollen diatoms and coccal green algae An age model is based on 21 calibrated AMS radiocarbon dates from terrestrial plants The sedimentary record covers the entire Holocene period Trophic status and circulation/stagnation patterns of the lake were inferred from algal assemblages the subannual structure of varves and the physicochemical properties of the sediment During the Holocene mixing conditions alternated between di oligo and meromictic depending on length and variability of spring and fall periods and the stability of winter and summer weather The trophic state was controlled by nutrient input circulation patterns and the temperaturedependent rates of organic production and mineralization Climate shifts mainly in phase with those recorded from other European regions are inferred from changing limnological conditions and terrestrial vegetation Significant changes occurred at 11600 cal yr BP Preboreal warming between 10600 and 10100 cal yr BP Boreal cooling and between 8400 and 4550 cal yr BP warm and dry interval of the Atlantic Since 4550 cal yr BP the climate became gradually cooler wetter and more oceanic This trend was interrupted by warmer and dryer phases between 3440 and 2850 cal yr BP and likely between 2500 and 2250 cal yr BPDespite decades of research there are still many open questions concerning the variability of the Holocene climate in Central Europe Reasons are uncertain chronologies large distances between investigated sites and lack of understanding of the regional effects of climate change especially of changing seasonality

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