Decadal hydroclimate fluctuations recorded in lake sediments from northeastern Iran over the past 1350 years

Hydroclimatic variability has significantly influenced societal dynamics in arid Central Asia (ACA), by triggering periods of unrest and migration. The western part of ACA, a key node of the ancient Silk Roads, remains poorly investigated due to limited climatic and environmental records, hindering our understanding of how environmental changes shaped the evolution of civilization in this region. This study uses records of high-resolution scanning XRF (X-Ray Fluorescence), n-fatty acids, and grain size from the sediments of Green Spring Lake, in northeastern Iran, within the historically prominent region of Greater Khorasan. This record is then used to reconstruct the regional hydroclimatic variability over the past 1,350 years. It reveals a generally dry and stable climate during the Medieval Climate Anomaly (950–1250 CE), a pronounced drought during 1250–1350 CE, and a transition to wetter conditions accompanied by increased hydroclimatic variability during the Little Ice Age (1400–1850 CE). During the LIA, increased moisture supply to northeastern Iran was caused by a negative NAO phase in spring, coupled with anomalous ascending atmospheric motion caused by the weakening of the Siberian High, which jointly led to increased spring precipitation in this region. Additionally, drought events during 970–1040 CE, 1220–1250 CE, 1480–1520 CE, 1600–1650 CE, and 1850–1910 CE align with documented events in eastern Iran, including severe famines and population declines, as recorded in historical Iranian sources.