Growth indices of North European Scots pine record the seasonal North Atlantic Oscillation

A network of 30 ring-width chronologies of Scots pine (Pinus sylvestris L.) from various parts of the boreal forest belt in north Europe were calibrated against seasonal indices of the North Atlantic Oscillation (NAO). The northernmost pines, from the forest-limit region, proved to be sensitive to summertime variations of the NAO, while most southern pines respond to winter variations in the NAO index. Going from the north to the south, growth responses demonstrate that this drastic shift occurs directly south of the northern part of the boreal belt. The southern part of the pine network was used for building a transfer model of wintertime NAO between 1893 and 1981. Although the final model explains only one quarter of the variance of the predictand winter NAO index, the verification statistics show reasonable reconstruction skill. This preliminary work will complement the increasing number of proxy experimental reconstructions of the NAO.