XVI INQUA Congress
Paper No. 48-5
Presentation Time: 9:30 AM-9:50 AM

HOLOCENE ANNUAL MEAN TEMPERATURE CHANGES IN THE BOREAL ZONE OF EUROPE: POLLEN-BASED RECONSTRUCTIONS

SEPPÄ, Heikki1, ANTONSSON, Karin1, HEIKKILÄ, Maija2, and POSKA, Anneli3, (1) Department of Earth Sciences, Uppsala Univ, Villavägen 16, Uppsala, 75236, Sweden, heikki.seppa@geo.uu.se, (2) Department of Geography, Univ of Helsinki, P.O. Box 64, Helsinki, 00014, Finland, (3) Institute of Geology, Tallinn Technical Univ, Estonia pst. 7, Tallinn, 10143, Estonia

Holocene annual mean temperature (Tann) trends were reconstructed from radiocarbon-dated pollen stratigraphies from lake sediments in Estonia, Finland, and Sweden. The reconstructions were carried out using two North-European pollen-climate calibration models based on weighted averaging partial least squares regression. Palaeotemperatures from Estonia and Finland were reconstructed with a model where the cross-validated prediction error is 0.89oC and the coefficient of determination between observed Tann values and those predicted by the model is 0.88. Reconstructions from Sweden were carried out with a model with the prediction error 0.95oC and coefficient of determination 0.88. In the reconstructions, Holocene thermal maximum (HTM) is distinguishable at 8000 - 4500 cal yr BP, with Tann on average 2.5oC higher than at present. The pollen-stratigraphical data reflects progressively warmer and drier summers during the HTM. Analogously with the modern decadal-scale climatic variability in North Europe, we interpret this as an indication of increasing climatic continentality due to the intensification of anticyclonic circulation. Post-HTM cooling started at around 4500 cal yr BP. All reconstructions show a transient cooling of 1.5 - 2.0oC at 8500 - 8100 cal yr BP, caused predominantly by the declines of Corylus, Ulmus, and Alnus. We correlate this cold event with the North-Atlantic 8.2 ka event. Provided that the 8.2 ka event was caused by freshening of the North-Atlantic surface water, our data provides evidence of the climatic responsiveness of the boundary of the boreal and temperate zones to the weakening of the North-Atlantic thermohaline circulation and the zonal energy transport over Europe. No other cold events of comparable magnitude are indicated during the last 8000 years.

XVI INQUA Congress
General Information for this Meeting
Session No. 48
Warm Times/Cold Times: Holocene Climate Variability in the North Atlantic Region
Reno Hilton Resort and Conference Center: Crystal 3&4
8:00 AM-12:00 PM, Monday, July 28, 2003

Geological Society of America Abstracts with Programs, , p. 157

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