Evidence for effects of solar forcing and North Atlantic circulation on the climate of continental Scandinavia during the Holocene

Nearly 10 000-year-long varved sediment records from Lakes Nautajärvi and Korttajärvi, Finland, analyzed using digital image analysis techniques, provide evidence of climate and environment oscillation at multi-decadal to millennial timescales. We used two independent methods, the REDFIT periodogram analysis and the Posterior Singular Spectrum Analysis, to extract the periodic features of time series from clastic laminae and assess their statistical reliability. The analyses revealed that seasonal sediment fluxes correspond with environmental changes with significant periodicities of 1500-1800, 1000, 600-800, nearly 300, nearly 200, 150-170, nearly 90 and 47 years, showing variable coherency with different climate forcing factors and other palaeoproxy records in the Northern Hemisphere. The results indicate that the Holocene winter climate in continental Scandinavia was forced by a combination of several factors, at least by solar variability and the North Atlantic ocean-atmosphere circulation patterns, with a varying influence through time.