Reconstruction of summer temperatures from tree-rings of Scots pine (Pinus sylvestris L.) in coastal northern Norway

Abstract

At the coast of northern Norway, 69°N, tree-ring chronologies from Scots pine (Pinus sylvestris L.) were constructed at Forfjorddalen in the Vesterålen archipelago (AD 1358-1992), Stonglandseidet on Senja (AD 1548-1994) and Vikran near Tromsø (AD 1700-1992). All chronologies reflect July-August temperatures. At the most northern site, Vikran, the response was more confined to July temperatures, resulting in a strong tree-ring and climate signal. The chronology from a steep, south-facing slope at Stonglandseidet showed signs of drought sensitivity. At the most oceanic locality, Forfjorddalen, mild winters appear to suppress tree growth on a decadal scale. Growth variations were consistent between the three sites for 1700-1910 but the amount of low-frequency variability decreased towards the most oceanic site. The seventeenth century, the coldest period of the ‘Little Ice Age’, experienced three cycles of summer temperatures, with minima around 1605, 1640 and 1680. An extended warm period occurred around 1475-1540. Temperature reconstruction showed secular trends similar to those observed east of the Scandes, but differed in the magnitude and timing of the extremes. At Forfjorddalen, there was no evidence of pine regeneration around 1575-1650. The latter site is likely to have been affected by logging activity in the seventeenth century.