Bioclimatic change of the past 2500 years within the Balkhash Basin, eastern Kazakhstan, Central Asia

On the bases of analytical data of an 850-cm-long sediment core collected from Balkhash Lake with a chronological control of seventeen AMS dates, this research reconstructed the lake salinity using carbonate content and the oxygen isotopic composition as proxies and reconstructed the basin-wide moisture using A/C ratio and pollen concentration as proxies. Basin-wide mean annual temperature (MAT) and mean annual precipitation (MAP) were reconstructed using climate-pollen response surface method. The reconstruction appears to be supportive to the early proposition that the climate in the westerlies-dominated areas has been generally characterized by cool-wet and warm-dry modes. Balkhash Basin has experienced three stages of climate change during the past similar to 2500 years: cool-wet from similar to 2500 to similar to 1800 cal. BP, moderate from similar to 1800 to 650 cal. BP, and cooling and wetting during the past similar to 650 years with the past similar to 100 showing warming and drying. The moisture evolution has closely followed the MAP variation and the MAT must have modulated the moisture evolution through controlling the evaporation. The first-order variation in lake salinity has been controlled by basin-wide temperature, i.e., low temperature raises the salinity level in the lake through reducing the ice-melt water supply to the lake. The second-order variation in the lake salinity seems to be modulated by pronounced variations in basin-wide moisture. Those low-amplitude variations in basin-wide moisture levels left no detectable imprints in lake salinity proxy records. (C) 2013 Elsevier Ltd and INQUA. All rights reserved.