Minskad trädtillväxt under Lilla sitiden? : En dendroklimatologisk jämförelse mellan nutid och 1600-talet invid trädgränsen i norra Skandinavien
2015
Axelsson, Pia
During the period called Little Ice Age (1400 ~ 1900) the climate of northern Europe was in an annual year-basis overall colder than it was before and after that period. The numbers of short, cold and rainy summers and long, bitter-cold winters where often repetitive under the approximately 500-years the period lasted. In Scandinavia, the coldest time during this period is estimated to have started around the end of the 16th century and lasted to the beginning of the 18th century. Trees growing at the tree-line are limited by temperature for their annual growth and hence showing differences of growth during changes in the climate, a method called dendroclimatology. The variations of growth can be read in the tree-rings either by analyze the width of the ring or by look into the density of the wood and is used to reconstruct past climates. The aim of this study is to investigate how the tree-growth responded to the colder temperatures compared to today. Trees (Scots pine) close to the tree-line in northern Scandinavia where used to enhance the temperature signal in the data. The proxy used is the growth density (MXD – maximum latewood density). The result reveals that during the coldest century, the trees show a larger number of negative growth-years with comparison with the 20th century and the negative and positive growth follows a more united trend. The result also shows a great number of negative growth-years at the end of the Little Ice Age, with a lot of extreme low growth - indexes (lower than -1.5). The conclusion then leans towards a cooler climate with overall lower temperatures under the 17th century compared to 1900-2004.
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