TEMPORAL STABILITY OF CLIMATIC SIGNAL RECORDED BY STABLE CARBON ISOTOPE COMPOSITION OF TREE RINGS α-CELLULOSE—A CASE STUDY FOR SUWAŁKI REGION

ABSTRACT Investigations of stable carbon isotope composition in α-cellulose extracted from tree rings of pines ( Pinus sylvestris L.) growing in the unpolluted Suwałki region, northeastern part of Poland, are undertaken. The presented carbon isotope record covers the period of 1931–2003. Values of δ 13 C measured in the tree ring α-cellulose are compared to meteorological data. These δ 13 C values in tree ring cellulose respond to summer temperature, insolation, relative humidity, and precipitation. The best correlation is observed between relative humidity and carbon isotope data. The August relative humidity is found more influential on δ 13 C values than relative humidity for any other month or combination of months (r = –0.65). Relations between isotopic and meteorological data demonstrate that precipitation influences the stable carbon isotopic ratios to a lower extent than humidity. The intensity and duration of summer rainfall events can determine this effect. The temporal stability of climate-proxy connections is an important issue in paleoclimatic reconstruction. Therefore, the temporal stability of climatic signals recorded by stable carbon isotopes is analyzed in this research using the moving correlation function for moving intervals with a 25-year window. Based on those investigations the highest time stability of correlation was found for the carbon isotope and the August relative humidity. More variability is observed for the correlation of δ 13 C values with precipitation.