HOLIVAR2006 Abstracts
Seasonal air-temperature anomalies in relation to 4000 years of land-use in the southern Austrian Alps.
R. Schmidt1, C. Kamenik2 and M. Roth1
1Institute of Limnology, Austrian Academy of Sciences, Mondseestrasse 9, A-5310-Mondsee, Austria
2Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland
Contact: R. Schmidt (roland.schmidt@oeaw.ac.at)
Diatom and chrysophyte cyst-based reconstructions of the dates of spring and autumn lake-mixing enabled us to infer spring and autumn temperature anomalies of the last 4000 years at the southern slopes of the Austrian Central Alps. On average, spring and autumn temperatures were lower during the two millennia BC when compared with 0 to 1500 AD Spring-temperature anomalies during Roman and Medieval times equaled or exceeded the modern value, and paralleled tree-line and glacier fluctuations. Marked spring-temperature minima occurred at about 1300 and 600 BC and during Late Medieval times. These major climatic oscillations, together with Medieval warming from 1000 to 1300 AD, corresponded with atmospheric residual 14C. The inferred autumn-temperature anomalies showed a narrower range than those during spring. Nevertheless, they indicated an increase during Medieval times. Together with a decline in beech pollen, this may indicate an increase in continentality. Seasonal climate change during Roman and Medieval warm periods seems to differ from the change observed during modern times probably due to changes in circulation modes. Four pulses of alpine land-use, derived from indicator pollen, occurred during (1) Early to Late Bronze, (2) the transition from Late Bronze to Early Iron Age (Hallstatt), (3) Late Iron Age (La Tène, Celtic time) to Roman times, and (4) during Late Medieval times. Climate seemed to be an important trigger of alpine land-use. It could, however, not be reduced to a simplistic view of climatic determinism.
Roland Schmidt is professor for palaeolimnology at the Institute of Limnology of the Austrian Academy of Sciences in Mondsee, Austria. His research interest focuses on diatom and chrysophyte cyst-based quantitative reconstructions of climatic and environmental variables and multi-proxy studies of Austrian Alpine lakes.