Tree ring-based temperature reconstruction, and the influence of the NAO on growth patterns of scots pine in west central Jämtland

Abstract

The development of tree ring chronologies is an important process in research of past climates. In this study a new tree ring width (TRW) chronology from west central Jämtland is presented with the aim of reconstructing a series of a climate variable, together with an analysis of the influence of Atmospheric Circulation, specifically of the North Atlantic Oscillation (NAO) on the growth patterns of sampled trees. A significant mean temperature-growth relationship for June-July was found and a new temperature series was subsequently reconstructed. The reconstructed temperature series showed interdecadal variability consistent with previous tree ring studies in Jämtland. However, it did not capture the observed warming trend of the 20th century, a problem which can occur in tree ring studies carried out at high latitudes. Significant, but not very strong statistical relationships were found between the NAO, as well as the summer North Atlantic Oscillation (SNAO), and the tree growth. Running correlation analysis between the SNAO-index and the chronology demonstrated that the strength of their relationship is not stable through time.