High-resolution hydroclimatic variability in northern Inner Asia in response to North Atlantic temperature changes during the last 2500 years

The North Atlantic climate has been suggested to exert a major control on the hydroclimate of Inner Asia, but the direction and persistence of the temperature–moisture relationship remain unclear. Here, we present new varve-chronology-constrained geochemical and mineralogical records from Lake Shira in northern Inner Asia, revealing a cyclical succession of centennial-scale wet-dry climate intervals over the past ∼2500 years. Wet periods with high lake levels are interrupted by three arid intervals (350–479 CE, 1459–1534 CE, 1898–1928 CE), marked by low lake levels, high salinity and holomixis. The wet intervals coincide with the Roman Warm Period, the Medieval Warm Period and the middle–late Little Ice Age (LIA), and the dry phases with cold spells associated with the Dark Ages Cold Period and the beginning and end of the LIA. A phase of less intense aridity 349–296 BCE overlaps with the end of the Iron Age Cold Period. A thorough review of published climate data and our own findings shows that this pattern is primarily driven by thermal conditions in the North Atlantic region, where higher sea surface temperatures (reflected in elevated Atlantic Multidecadal Oscillation indices) promote more positive North Atlantic Oscillation states and intensify mid-latitude westerly moisture transport. Comparison of varve thickness measurements with observed/reconstructed climate records for the past 150 years indicates that sedimentation rate is mainly controlled by fluvial discharge to the lake. Although varve thickness tends to be negatively correlated with precipitation and temperature, several notable exceptions limit its use as independent climate proxy.