Aeolian sediment in raised bog deposits, Halland, SW Sweden: a new proxy record of Holocene winter storminess variation in southern Scandinavia?

Abstract

Cores of peat taken from two raised bogs in the near-coastal part of Halland, SW Sweden, were examined for their content of wind-transported clastic material. The Boarps Mosse core has a length of 262 cm and covers the last 2850 years (age model based on three radiocarbon dates), while the Hyltemossen core has a length of 347 cm and records the last 7000 years (age model based on eight radiocarbon dates). The peat contains aeolian quartz silt and sand (from trace amount to more than 10 weight /% of the dry peat sample), and the grain-size composition of the minerogenic sediment indicates that the material is composed of both far-travelled dust and local wind-eroded silt and sand. Grains larger than 0.2mm are present in many intervals and probably record niveo-aeolian transport in connection with severe snowstorms. A systematic count of quartz grains between 0.2-0.35mm and larger than 0.35mm was carried out to determine variations in aeolian sand influx (ASI) and winter wind climate with time. The Boarps Mosse site is situated in a hilly terrain and is primarily open to southerly and northerly winds, while the Hyltemossen site is situated in a more flat landscape open to winds from most directions. Furthermore, at Boarps Mosse dense forest stands seem to have protected the site from significant aeolian sand influx until about AD 1000, while aeolian sand influx apparently was less influenced by local forest development at Hyltemossen. However, using periods with low ASI values as marker horizons it is possible to identify a number of periods of high ASI values during the last 2500 years. These periods, which probably record high winter storminess, are dated to 130, 300, 400, 475, (700), 900, (1000), (1100), (1150), (1350), (1450), 1675, (1800), 1875, 1950-2000, (2050), 2150, 2225 and (2300) cal. yr BP. In addition, the Hyltemossen site documents peak storminess at 2450, 2725, 2850-3050, 3275, 3675, 4100-4200, 4550, 4900, 5100-5200 and 5450-5700 cal. yr BP. Most of the aeolian activity phases in Halland correlate with well-known cold periods in northwest Europe, suggesting a link between winter storminess in southern Scandinavia and expansion of the polar vortex.