ИСТИНА

The tree-ring spruce (Picea abies (L.) Karst and Picea obovata Lebed.) network was developed on the Solovki Islands (64.5-65.1 N – 35.3-36.1 E). The climate of the Solovetsky Archipelago located in the White Sea is quite severe (summer temperature +12.9 ⁰C, winter temperature -8.5 ⁰C, annual precipitation 480 mm, length of the vegetation period is about 128 days). The spruce tree-ring network in Solovki includes 12 sites. More than 140 tree-ring samples were successfully cross-dated and standardized by negative exponential curve. The composite spruce chronology covers the period of 1626-2012 ss. (with sample depth more than 5). For the response function analyses we used the monthly mean temperature and precipitation from Kem-Port weather station (1896-2012 ss.). Climate response function was calculated using TreeClim software (Zang and Biondi, 2015). The analysis showed that spruce growth at most sites is controlled by June air temperatures (the coefficients of correlation varied from 0.3 to 0.6). Composite chronology also revealed high enough correlation with June temperatures (R=0.6, p<0.05) with statistically significant temporal stability over the period on instrumental records proved by the TreeClim analyses of the moving correlation. The linear model based on this relation passed all statistical tests (positive Reduction of Error and Coefficient of Efficiency) indicating that spruce ring-width chronology is suitable for further temperature reconstruction. A June temperature reconstruction covers the period of 1673-2012 ss. Based on 20-year smoothed reconstruction, the cold anomalies date back to 1673-1692, 1767-1825, 1835-1904, and the warmings occurred in 1693-1766, 1826-1834. Response function analysis of the local and composite chronologies also showed increased correlation (R=0.64, p<0.05) between ring-width chronologies and June temperatures in the years when the positive phases of the summer NAO had occurred. Strong relationship, most likely, is due to the appearance of more favorable climatic conditions for tree-ring growth associated with above-average temperatures (and above-average precipitation) over the northern Europe when the North Atlantic Oscillation was in the strong positive phase. The study was funded by the Russian Scientific Foundation N 17-77-20123.