New evidence of Holocene atmospheric circulation dynamics based on lake sediments from southern Sweden: a link to the Siberian High F. Muschitiello a, * , L. Schwark b , B. Wohlfarth a , C. Sturm a , D. Hammarlund c a Department of Geological Sciences, Stockholm University, 106 91 Stockholm, Sweden b Institute of Geosciences, University of Kiel, Ludewig-Meyn-Str.10, 24118 Kiel, Germany c Department of Geology, Lund University, Sölvegatan 12, 223 62 Lund, Sweden article info Article history: Received 15 April 2013 Received in revised form 12 July 2013 Accepted 16 July 2013 Available online Keywords: Lake sediments Stable isotopes Sweden Holocene Palaeoclimatology Atmospheric circulation Siberian High abstract Oxygen (d 18 O) and carbon (d 13 C) isotope records of calcitic carbonate components (Chara sp. algal en- crustations and Bithynia tentaculata gastropod opercula) from a lake-sediment succession on the Baltic Sea island of Gotland, south-eastern Sweden, have been obtained to investigate regional climate dy- namics during the Holocene. The hydrological sensitivity of the small lake, particularly in terms of spring snowmelt contribution to the local water budget, provides a means of tracing past changes in the in- fluence of snow-bearing easterly winds across the Baltic Sea Proper, which signifies the wintertime strength of the Siberian High. Repeated episodic depletions in 18 O at the centennial scale correlate with events of increased potassium concentration in the GISP2 ice-core record from Greenland, which in- dicates a coupling to large-scale fluctuations in atmospheric circulation patterns. A corresponding cor- relation with simultaneous depletions in 13 C suggests repeated responses of the local lake hydrology to snow-rich winters through decreasing water residence time, perhaps augmented by methanogenesis due to prolonged ice-cover seasons under the influence of an expanding Siberian High. Frequency analysis of the isotopic records reveals well-defined fluctuations at quasi-500-520-, 670-, 830- and 1430- yr periodicities, and a gradually stronger impact of Polar air outbreaks across the southern Baltic Sea region with time after ca 6000 cal. BP. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The North Atlantic atmospheric system plays a key role in North European climate (Luterbacher et al., 2002). Precipitation is closely related to the passage of cyclones that normally follow a west-east trajectory across Scandinavia. The highest amount of precipitation is registered on the windward, western side of the Scandinavian Mountains, with decreasing air-mass penetration eastwards lead- ing to drier conditions in the interior regions. North European climate variability and associated changes in air mass trajectories are often attributed to the North Atlantic Oscillation (NAO) (Hurrell et al., 2001), but regional climate is also strongly influenced by the Siberian High. This is frequently the case in winter when a high- pressure ridge associated with the Siberian anticyclone extends across Scandinavia, bringing cold and dry easterly winds. These collect moisture from the Baltic Sea and generate strong snowfall along the Baltic Sea coast of eastern Sweden (Yu and Harrison, 1995; Uvo and Berndtsson, 2002; Uvo, 2003). Present-day atmo- spheric circulation dynamics are well understood, but knowledge of past changes in circulation patterns, and especially their regional impact, still lacks sufficient detail. Stable-isotope analyses of lake sediments, based primarily on d 18 O of carbonates (Hammarlund et al., 2002; Rosqvist et al., 2007), silica (Rosqvist et al., 2004), or aquatic cellulose (St. Amour et al., 2010), have been successfully employed in Sweden during the last decade to reconstruct past atmospheric circulation dynamics on multiple timescales. For example, these studies allowed for reconstructing past regional changes in the dominant airflow pattern and associated moisture variations (Hammarlund et al., 2002; Rosqvist et al., 2004, 2007; Jonsson et al., 2009; Andersson et al., 2010; St. Amour et al., 2010). As shown by these studies of open-basin lakes, the inferred lakewater oxygen-isotope composi- tion mirrors d 18 O of the dominant input water component, usually precipitation (d 18 O p ), although this may be biased by groundwater and snowmelt contributions. By using a multi-proxy approach involving multiple lacustrine carbonate components, Hammarlund et al. (2002) found a devia- tion from the modern Dansgaard-type d 18 O p -temperature relation * Corresponding author. E-mail address: francesco.muschitiello@geo.su.se (F. Muschitiello). Contents lists available at ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev 0277-3791/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.quascirev.2013.07.026 Quaternary Science Reviews 77 (2013) 113e124