Climate and Environmental Changes over the past 150 Years Inferred from the Sediments of Chaiwopu Lake, Central Tianshan Mountains

Arid regions are predicted to be among the ecosystems most affected by global climate change. Evaluation of the responses of arid environments to global climate requires further data collection, experimental work, modeling, and interdisciplinary exchange to improve the understanding of climate–ecosystem interactions at various spatial and temporal scales.

Chaiwopu Lake, located in the central area of the Tianshan Mountains, Xinjiang, northwest China, possesses a sensitive ecological zone. In the past 30 years, the lake has undergone great changes in water surface area, resulting in some serious environmental impacts on this ecologically vulnerable, continental, arid region.

To investigate climate and environmental changes in Chaiwopu Lake over the past 150 years, MA Long et al. developed a sediment age–depth model using 1³⁷Cs. They compared temporal changes in several sediment variables with recent meteorological and tree-ring records.

The results showed that organic matter had a positive correlation with the Palmer Drought Severity Index in the central Tianshan Mountains, and the δ¹³C of organic matter had a positive correlation with regional temperature. They applied constrained incremental sum-ofsquares cluster analysis to element concentrations in the core and identified three distinct zones: (1) 55–46 cm, ~1860–1910; (2) 46–26 cm, ~1910–1952; and (3) 26–0 cm, 1952–present.

Between 1880 and 1910 AD, following the Little Ice Age (LIA), the sediment environment was relatively stable, climate was cold and dry, and the lake water displayed high salinity, in contrast to conditions during the LIA. During the LIA, westerlies carried more water vapor into Central Asia when the North Atlantic Oscillation was in a negative phase, and encountered the enhanced Siberia High, which probably led to increased precipitation. In the period 1910–1950 AD, the lake was shallow and the regional climate was unstable, with high temperatures and humidity. In the last ~15–20 years, human activities caused an increase in sediment magnetic susceptibility, and heavy metal and total phosphorus concentrations in the sediment were substantially enriched.

Mean annual temperature displays a warming trend over the past 50 years, and the lowest temperature was observed in the 1950s. There has been an increase in annual total precipitation since the 1990s. The combined influences of climate and human activity on the lake environment during this period were faithfully recorded in sediments of Chaiwopu Lake.

This study provides a scientific basis for environmental management and protection. The result was published inInternational Journal of Earth Sciences in April 2013, 102: 959-967.