Indirect influence of the Siberian high on the increased annual temperature range in southern Northeast Asia since the late 19th century: Insights from tree-ring δ¹⁸O

Current dendroclimatological reconstructions based on tree-ring oxygen isotopes (δ¹⁸O) predominantly focus on climate variability during the growing season and at annual timescales. However, climate conditions during the non-growing season and their associated driving mechanisms remain insufficiently understood. To address this research gap, we developed a 349-year tree-ring δ¹⁸O series using four Pinus tabuliformis samples growing near Beijing in southern Northeast Asia (SNA), enabling the reconstruction of winter-spring minimum temperature variations from 1674 to 2022 CE ( r = 0.648, p < 0.0001, n = 54). The results indicate a cooling trend in the study area from 1674 to 1892 CE, followed by a warming trend from 1893 to 2022 CE. However, the mean temperature during the earlier cooling period was higher than that of the subsequent warming period. By subtracting our reconstructed winter-spring temperatures from previously published summer temperature reconstructions in the SNA—serving as an approximation of the annual temperature range—we observe a persistent increase in annual temperature variability since the late 19th century. The reconstructed temperature variability is primarily modulated by the intensity of the Siberian High, indicating strong control by large-scale atmospheric circulation. This study not only provides novel insights into the role of non-growing season climate in long-term climate dynamics, but also offers a valuable baseline for predicting future extreme climate events.