1. Evolution of northern wetlands since the Last Glacial Maximum Pirita Oksanen, University of Bristol, School of Geographical Sciences Contact p.oksanen@bristol.ac.uk. Wetland data synthesis web site http://www.bridge.bris.ac.uk/projects/deglaciation/wetlands.htmlp.oksanen@bristol.ac.uk http://www.bridge.bris.ac.uk/projects/deglaciation/wetlands.html 17000 cal BP 16000 cal BP 15000 cal BP 14000 cal BP 13000 cal BP 12000 cal BP 11000 cal BP 10000 cal BP 9000 cal BP 8000 cal BP 7000 cal BP Introduction Information from ca. 3000 late-Quaternary peat cores at above 39 N has been collected in a global wetland database within the QUEST-Deglaciation project. The data, including modern wetland type and area as well as peat stratigraphy and dating, are still incomplete, but most cores comprise at least the basal date indicating the time of wetland initiation. The synthesis is carried out in order to document the evolution of wetlands since the Last Glacial Maximum, to better understand the patterns of wetland initiation and the role of wetlands in the terrestrial carbon cycle during the last Ice Age and deglaciation, and to identify gaps in the existing wetland research. The data set will also be used to validate Earth System model simulations. Based on the collected data, a set of maps and time series is created, showing the change in peatland initiation and extent through time. All dates are calibrated to calendar years BP using OxCal calibration programme. The study area is divided into regions that show differences in the pattern of peatland evolution. Analyses on different characteristics are underway. Acknowledgements Earlier databases by Gorham et al. (2005) and McDonald et al. (2006) are incorporated into this database. The ice sheets reconstructions are based on ICE- 5G by Peltier (2004). Continental outlines are compiled by P. Bartlein. Results There was no significant peat accumulation in the high-latitudes of the northern hemisphere during the Last Glacial Maximum. Deglaciation started in America at ca. 16,000 cal BP, and first peatlands appeared at the same time. In Europe, deglaciation started earlier, at about 18,000 cal BP, but first peatlands are recorded at around 14,500 cal BP. Most of the early peatlands in America are now buried. In non-glaciated Alaska the formation started at ca. 17,500 cal BP, but in Siberia considerably later, at ca. 14,000 cal BP. At its most active peatland initiation was between 11,000 and 9000 cal BP: the highest peak in America occurred at ca. 10,500 and across Eurasia at ca. 9000 cal BP. Half of the glaciers had melted from Europe by ca. 15,000 cal BP, and by ca. 10,000 cal BP from America. For peatlands, the half point was reached at 8000 and 9000 cal BP, respectively, and in Siberia, at 8500 cal BP. By around 7000 cal BP, when 60% of the modern peatlands existed, the distribution pattern was similar to today. The biggest relative troughs in the initiation curves occur at ca. 12,000 cal BP in Europe and eastern North America, 11,500 cal BP in Alaska, ca. 8500 cal BP in western North America, 7500 cal BP in eastern Siberia and 7000 cal BP in western Siberia. None of these troughs extend below the standard deviation. Region together with mire type predicts best the age of a peatland or peat layer, but the variability is still large. Bogs show generally more constant accumulation rates than fens. Altitude makes little difference; most peatlands are located at lowlands, but peat of all ages is found at high altitudes too. All sites currently in the database, and division into regions. Extent of glaciers and distribution of peatlands through time Peatland initiation start and rates compared for the regions Peatland initiation dates and area covered by glaciers, for the world above 39 N and the regions Age-depth comparison of European bogs and fens