Summer temperature variations in southern Kamchatka as reconstructed from a 247-year tree-ring chronology of Betula ermanii

We have developed a 247-year ring-width chronology of Betura ermanii Cham. growing in an open canopy forest close to the tree line at a coastal site in southern Kamchatka. Climatic response analyses revealed that the ring width was primarily controlled by July-August temperature. The regression models that we used for statistical reconstruction passed the stringent calibration-verification tests used in dendroclimatology, resulting in the first quality-controlled tree-ring reconstruction for southern Kamchatka. The reconstructed temperature shows a cool period from the 1830s to the 1880s, followed by gradual warming until ca. 1940, then a cooling trend extending to the 1970s, and finally a warming trend continuing to the present. Spatial correlation analyses with sea surface temperature in the North Pacific indicated that the seas surrounding the Kamchatka peninsula play a role in modulating temperature variations in the study area whereas the effects of the Pacific Decadal Oscillation are relatively weak.