HOLIVAR2006 Abstracts
Holocene storminess variation and landscape dynamics in Halland, SW Sweden.
R. De Jong1, S. Björck1 and L.B. Clemmensen2
1GeoBiosphere Science Centre, Quaternary Sciences, Lund University, Sölvegatan 12, SE-22362, Sweden
2Geological Institute, Copenhagen University, Østervoldgade 10, DK-1350 Copenhagen, Denmark
Contact: Rixt de Jong (rixt.de_jong@geol.lu.se)
The coastal zone of Halland, SW Sweden, is strongly affected by the position and strength of Westerlies, since it lies in the region in which storm tracks shift position (Lamb 1977). Therefore, ombrotrophic peat bogs in this region are expected to hold a record of long term variations in the pathway and intensity of cyclones. Since the landscape of southern Sweden has also been affected by humans for a long time (Berglund 2003), human impact on vegetation and landscape has to be taken into account in multi proxy climatic reconstructions for this region.
In this study two ombrotrophic peat bogs in the coastal zone of Halland, SW Sweden, are examined for wind transported mineral grains, pollen, and humidity indicators. Mineral grain influx, interpreted as aeolian sand influx (ASI), was used as a proxy for storm frequency and intensity. It is thought that in order to transport large sand particles to the central part of a raised bog, niveo-aeolian conditions are required (Björck and Clemmensen 2004). If correct, this would imply that the ASI record may be used as a proxy for winter storminess. Since human activities may also affect the ASI record, pollen analysis is used to reconstruct human impact and landscape openness.
Results from both study areas indicate that ASI has fluctuated strongly during the past 6500 years, with peak influx values recorded around 4200, 2800-2400, 1500, 1100 and 700-100 cal. yr BP (De Jong et al. in press). Interestingly, the influx records for medium to coarse sand grains are remarkably similar at both sites and a tentative correlation with well-known climatic coolings in the North Atlantic region appears. Increases in the finer fraction of the mineral content, however, seem to be related to human impact and may reflect increased soil erosion due to intensified land use.
Berglund, B.E., 2003. Human impact and climate changes – synchronous events and a causal link? Quaternary International 105, 7-12.
Björck, S., Clemmensen, L.B., 2004. Aeolian sediment in raised bog deposits, Halland, SW Sweden: a new proxy record of Holocene winter storminess variation in southern Scandinavia? Holocene 14, 677-688.
De Jong, R., Björck, S., Björkman, L., Clemmensen, L.B., in press. Storminess variations during the last 6500 years as reconstructed from and ombrotrophic bog in Halland, SW Sweden. Journal of Quaternary Science.
Lamb, H.H., 1977. Climate, past, present and future, vol.2. Methuen & Co., London, 835 p.