A tree-ring record of 500-year dry-wet changes in northern Tibet, China

Abstract

Drought variability of the Tibetan Plateau is an important component across the Asian monsoon. Long-term information about the history of drought is, however, limited because the instrumental records are short. In this study we developed a tree-ring chronology of Sabina tibetica from northern Tibet and used it to reconstruct the history of drought variation for the region. Response analysis shows that water availability in spring and early summer is the main factor limiting the radial growth of Sabina trees in northern Tibet. A May–June Palmer Drought Severity Index (PDSI) reconstruction for the past 500 years ( r = 0.66, P < 0.0001) shows that the seventeenth century was the driest century, whereas the eighteenth, nineteenth and twentieth centuries were the wettest. The sixteenth century was not significantly different from the long-term mean. The major periods of reconstructed dry conditions include AD 1600–1610, 1617–1624, 1630–1632, 1639–1654, 1665–1681 and 1692–1701. Significant wetter periods were found to be AD 1520–1532, 1702–1705, 1716–1722, 1752–1758, 1839–1857 and 1928–1943. The drought rhythm in northern Tibet has three prominent periodicities: 2–7 and 130–200 years for the whole reconstruction and 16–24 years during the `Little Ice Age' (1520 to 1720). Two points of significant abrupt change in tree rings were found in years of 1530 and 1715, which may indicate the onset of dry and wet conditions during the `Little Ice Age'. There is an abrupt change around 1965, which may foreshow the beginning of regional prominent warming.