Solar forcing of desert vegetation and drought frequency during the last 2700 years in the interior Qaidam Basin, northeastern Tibetan Plateau

Abstract

Knowledge of long-term change in vegetation and climate in semi-arid/arid regions is essential for the study of current climate and development of mitigation strategies against severe drought. Here, a fossil pollen record of annually-varved core from Sugan Lake in interior Qaidam Basin was quantitatively analyzed to reconstruct changes in vegetation, floristic diversity and drought frequency. Results of biomization suggested that regional vegetation was desert vegetation with three short-term occupations of temperate steppe/xerophytic shrub during the last 2700 years. Floristic diversity generally increased/decreased with the expansion/degradation of desert vegetation. Moisture fluctuations showed three distinct stages (extremely dry between 742BC and ∼AD500, relatively wet with an increasing trend between ∼AD500 and 1200 and relatively wet with frequent fluctuations after AD1200), interrupted by 14 drought events. Spectral analysis and continuous wavelet transform of moisture variation revealed 200- and 120-year cycles. According to cross-wavelet transform analysis, major drought frequency of ∼200-year was explicitly correlated to solar activity. It’s suggested that the centennial-scale drought frequency was mainly driven by solar activity, through modulation of large-scale atmospheric circulation. Furthermore, the effect of surface temperature-evaporation and uplifting/subsiding air flow should be notable. The climatic drought in interior Qaidam Basin could be intensified under the continuous global warming.