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 ∼2500 years: cool-wet from ∼2500 to ∼1800 cal. BP, moderate from ∼1800 to 650 cal. BP, and cooling and wetting during the past ∼650 years with the past ∼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.