Rapid changes in the hydrological and temperature regimes over the past decades at the northern latitudes enhance significantly permafrost degradation accelerating carbon release, increase the frequency of drought events and extensive wildfires. However, the mechanisms and dynamics driving drought events and their influence on Siberian forests are currently the subject of numerous research activities. Newly developed and annually resolved stable carbon and oxygen isotope chronologies of larch tree-ring cellulose (δ¹³C_cell and δ¹⁸O_cell) for the period 516–2009 CE allowed the reconstruction of July precipitation and Arctic Oscillation (AO) in May, respectively. Unprecedented drought events occurred towards twentieth–twenty-first centuries as indicated by the July precipitation reconstruction. Positive AO phases in May were most pronounced during the second part of the first millennium, but also increased in frequency in the modern period of the twentieth–twenty-first centuries. Negative AO phases are associated with cold anomalies and show a remarkable decrease in the nineteenth century caused by a series of major volcanic eruptions. Our findings help explaining the increased frequency of Siberian forest fires over the past decades in Central Siberia consistent with a reduction of summer precipitation, triggered by a positive phase of the Arctic Oscillation in May.

过去几十年北纬地区水文和温度状况的快速变化显着加剧了永久冻土退化，加速了碳释放，增加了干旱事件和广泛野火的频率。然而，驱动干旱事件的机制和动力学及其对西伯利亚森林的影响目前是众多研究活动的主题。新开发并每年解析落叶松年轮纤维素（δ ¹³ C_细胞和δ ¹⁸ O_细胞）的稳定碳氧同位素年表) 在公元 516-2009 年期间，分别允许重建 7 月的降水和 5 月的北极涛动 (AO)。7 月降水重建表明，在 20-21 世纪之前发生了前所未有的干旱事件。5 月份的积极 AO 阶段在第一个千年的后半期最为明显，但在 20 至 21 世纪的现代时期频率也有所增加。负 AO 阶段与冷异常有关，并在 19 世纪由一系列主要火山爆发引起显着减少。我们的研究结果有助于解释过去几十年中西伯利亚中西伯利亚森林火灾的频率增加与夏季降水减少一致，这是由 5 月北极涛动的正相位引发的。