Variations in Sediment Grain Size from a Lake in the Tianshan Mountain of Central Asia: Implications for Paleoprecipitation Reconstruction

Abstract

The Tianshan Mountain is the largest mountain range in Central Asia, and the source area of many river systems. Changes in precipitation result in significant alterations to regional hydrological processes. Lake sediment from the Tian Shan representative of the last 90 years was chosen as the object of this research study. The grain-size data were used in conjunction with instrumental data to provide a method for determining changes in paleoprecipitation. The results showed the three-point moving average curve of the silty fraction content with a size of 16 to 32 μm to be significantly consistent with the curve of total precipitation from April to September since 1950. The total content of clay and fine-silty fraction (0–16 μm) was clearly consistent with the monthly precipitation in July. The total precipitation from April to September showed a significant downward trend from 1930 to 1975, and then an overall increasing trend beginning in 1975, which may have been influenced by the North Atlantic Oscillation. The change in precipitation reconstructed by the grain size of lake sediments was significantly different from the high-resolution gridded datasets (Climatic Research Unit Time-Series version 4.04) because of the lack of data from meteorological stations in China before 1950. The conclusions of this study are significant for evaluating the validity of climatic research unit (CRU) data in arid areas of Western China. In addition, the results of this study serve as a bridge between modern instrumental records and long time-scale paleoclimate research and provide important reference values for future reconstructions of long time-scale paleoclimate.

Keywords

• lake sediment
• grain size
• paleoprecipitation reconstruction
• Tianshan Mountain
• Central Asia