Tree-ring-based assessments of drought variability during the past 400 years in the Tianshan mountains, arid Central Asia

Abstract

In Central Asia, the frequency and severity of droughts have a strong impact on the climate and lives of people. Therefore, it is essential to explore climate change, especially its impacts on the cycle and extent of drought occurrence. To determine drought conditions, the Palmer drought severity index (PDSI) is diffusely implemented and can be reconstructed using tree-ring chronologies. We collected Schrenk spruce (Picea schrenkiana) cores from six distinct areas in the Tianshan Mountains and used them to establish tree-ring chronologies. Correlation and reaction research revealed that the main impact on tree growth was humidity from previous years and the present growing season. To reconstruct the historical PDSI for the Tianshan Mountains, chronologies were applied. The reconstructed PDSI was considered to describe the climate change in the Tianshan Mountains because it captured severe drought events that were observed in other research findings. Furthermore, the spatial analysis results covered almost all of the Tianshan Mountains at 0.5° resolution. A large-scale drought event in the 1910s that was prevalent in the Tianshan Mountains was detected with tree rings. The extreme drought years of 1917, 1919, and 1944 detected on the chronologies were also specifically verified. A decadal analysis showed that the eastern and western Tianshan Mountains experienced continuous drought in the 1880s and during the 1810s ~ 1830s, the central and western Tianshan Mountains experienced continuous drought in the 1770s and 1640s, while it experienced a continuous wetting in the 1750s, and large-scale wetting occurred in Central Asia in the 2000s. This research offers a new perspective on the instability and spatial spread of drought in the Tianshan Mountains.

Keywords

• Palmer drought severity index
• Long term drought variability
• Tree-ring width
• Tianshan Mountains