Tree growth responses to summer temperature on the Korean Peninsula detected by tree-ring blue intensity

Tree-ring blue intensity (BI), a relatively new proxy using the amount of blue light reflected from tree-ring cores, has garnered considerable attention in dendroclimatology due to its effectiveness in capturing climate signals. While the application of BI in climate reconstructions is spreading across the world, it has not yet been fully explored in East Asia. In this pilot study, tree-ring width (TRW) and BI (earlywood BI, maximum latewood BI, and delta BI) chronologies were developed from Korean pine (Pinus koraiensis Siebold & Zucc.) on Mt. Seorak in the Korean Peninsula. While the BI chronologies developed in this study exhibited relatively weak series intercorrelations, they nonetheless captured significant and consistent summer temperature signals, demonstrating their dendroclimatological potential. In particular, the delta BI (DBI) chronology was well correlated with summer (July to August) mean temperature at both local and regional scales. In contrast to the TRW chronology, which failed to capture a consistent climate-related signal, the DBI chronology consistently retained the tree growth response to summer temperature variability from the early 20th century to the present. Further large-scale correlation analysis demonstrated that the DBI chronology can be used in the historical reconstruction of the circumglobal teleconnection pattern and the subtropical jet stream. These findings show that the application of the BI methodology can significantly enhance the ability of tree-ring data to capture climate signals that are not apparent in TRW in subtropical East Asia.