Quantitative assessment of precipitation seasonality and summer surface wetness using ombrotrophic sediments from an Arctic Norwegian peatland

Seasonality of precipitation is an important yet elusive climate parameter in paleoclimatological reconstructions This parameter can be inferred qualitatively from pollen and other paleoecological methods, but is difficult to assess quantitatively. Here, we have assessed seasonality of precipitation and summer surface wetness using compound specific hydrogen and carbon isotope ratios of vascular plant leaf waxes and Sphagnum biomarkers extracted from the sediments of an ombrotrophic peatland. Bostad Bog, Nordland, Norway. Our reconstructed precipitation seasonality and surface wetness are consistent with regional vegetation reconstructions During the early Holocene. 11.5-7.5 ka, Fennoscandia experienced a cool, moist climate. The middle Holocene. 7.5-5.5 ka, was warm and dry. transitioning towards cooler and wetter conditions from the mid-Holocene to the present. Changes in seasonality of precipitation during the Holocene show significant coherence with changes in sea surface temperature in the Norwegian Sea. with higher SST corresponding to greater percentage of winter precipitation Both high SST in the Norwegian Sea and increased moisture delivery to northern Europe during winter are correlated with a strong gradient between the Subpolar low and subtropical high over the North Atlantic (positive North Atlantic Oscillation) (C) 2009 University of Washington Published by Elsevier Inc All rights reserved