Precipitation variations and possible forcing factors on the Northeastern Tibetan Plateau during the last millennium

Understanding precipitation variation, drought and flood history, and their associated forcing mechanisms are important to human society. In this study, five moisture-sensitive tree-ring width chronologies are used to represent variations in precipitation over the past millennium on the Northeastern Tibetan Plateau (NETP). We find a strong coherency between chronologies in the NETP, indicating a common response to regional climate during the last millennium. The first principal component of the five chronologies (PC1) correlates significantly with regional precipitation and can thus be used as an indicator of regional precipitation variations. Dry spells, even more severe than the 1920s drought, occurred during AD 1139–1152, 1294–1309, 1446–1503 and 1708–1726. Previous studies in this area using other proxies also identified these droughts. Multi-Taper spectral analysis demonstrates significant periodicities at 205 yr and 73 yr, plus a range of ~ 2 yr cycles, suggesting possible linkage with solar variation and the Pacific Decadal Oscillation (PDO). PC1 also shows coherent patterns with solar irradiance variation: the precipitation tends to reach low values during the well-known solar minimum.