Reconstruction of past storminess: Evaluation of an indicator approach using aeolian mineral grains buried in peat deposits, Estonia

This study aims to evaluate a reconstruction method of past storminess using aeolian sand influx (ASI) in peat deposits. We use high-resolution records of ASI from four peat bogs along the Estonian coast and compare those with local instrumentally-recorded storminess data since 1920 AD and with historical climatic records around the Baltic Sea over the last two centuries. Potential effects of local changes in forest cover and anthropogenic disturbances on the ASI signals are also evaluated with historical maps available for the study sites. Diameter of all sand grains >65 μm is measured with an image analysis system to detect temporal changes in the grain-size distribution. Our results demonstrate two major periods of high ASI over the last centuries in the region: during the 19th century and since the 1950s with highest values in 1980–2000 AD. Cross-correlations between the changes in ASI and the instrumentally-recorded storm days during the last century are positive and significant. High ASI values recorded during the 19th century correspond to the positive NAO indices and high cyclonic activity reconstructed in southern Sweden. We find that sand grains <250 μm in diameter add additional information for detecting changes in storminess. Temporal shifts in grain-size distribution and median diameter of mineral grains occur in every core, showing changes in the source materials through time.