From the CO2Science archive: What was done: Based on carbonate percentages and ostracode abundances found in sediment cores they extracted from Hurleg Lake in the arid Qaidam Basin of the Northeast Tibetan Plateau, the authors developed a history of precipitation-driven changes in lake level over the past 1,700 years, which they compared with a contemporaneous history of tree-ring-derived precipitation over surrounding mountainous terrain, as well as with changes in solar activity that were manifest in solar proxy residual Δ14C data.
Paper reviewed: Zhao, C., Yu, Z., Zhao, Y. and Ito, E. 2009. Possible orographic and solar controls of Late Holocene centennial-scale moisture oscillations in the northeastern Tibetan Plateau. Geophysical Research Letters 36: 10.1029/2009GL040951.
What was learned
Zhao et al. discovered that “carbonate percentage and ostracode abundance show a consistent pattern with ~200-year moisture oscillations during the last 1,000 years,” with the moisture pattern in the Qaidam Basin being “in opposite relation to tree-ring-based monsoon precipitations in the surrounding mountains, suggesting that topography may be important in controlling regional moisture patterns as mediated by rising and subsiding air masses in this topographically-complex region.” In addition, they found that cross-spectral analysis between their moisture proxies and the solar activity proxy “shows high coherence at the ~200-year periodicity which is similar to Chinese monsoon intensity records, implying the possible solar forcing of moisture oscillations in the NE Tibetan Plateau.”
What it means
Once again we have another real-world example of cyclical solar activity controlling the cyclical nature of precipitation variations, wherein, in the words of the researchers who conducted the study, “higher solar output corresponds to a stronger monsoon, which intensifies the uplift of air mass on the high Tibetan Plateau and strengthens the subsidence of air mass over the Qaidam Basin,” while “the reverse is true during the period of lower solar output,” so that “high solar activity is correlated with dry climate in the Qaidam Basin and increased precipitation in monsoonal areas.”