Hydroclimatic controls on lake water oxygen isotope in alpine lake on the northern Tibetan Plateau: Insights from isotope mass balance modeling

Study region: Bangkog Lake, a representative alpine lake on the northern Tibetan Plateau (TP). Study focus: This study investigates the controls on alpine lake water δ 18 O variability through monthly monitoring of stable isotopes ( δ 18 O and δ D) and meteorological parameters during 2019. An isotope-based mass balance model (MBM) was developed to simulate seasonal δ 18 O dynamics and systematically evaluate its sensitivity to key hydroclimatic drivers, aiming to improve the interpretation of δ 18 O records from TP alpine lakes for paleoclimate reconstruction. New hydrological insights: The calibrated MBM successfully reproduced observed δ 18 O variations (Nash–Sutcliffe Efficiency = 0.595, R 2 = 0.689), revealing a clear hierarchy of environmental controls. Evaporation was identified as the dominant driver of isotopic enrichment, with temperature exerting secondary influence, while precipitation amount and relative humidity demonstrated remarkably limited effects. The pronounced evaporative sensitivity, particularly during summer months, establishes lake water δ 18 O as a robust proxy for past aridity rather than precipitation variability. These findings underscore the importance of process-based modeling for accurate interpretation of isotopic archives from high-elevation lacustrine systems. • Isotope model quantifies seasonal δ 18 O changes in Tibetan Plateau lakes. • Lake water δ 18 O is driven by evaporation and secondarily by temperature. • Lake water δ 18 O can reflect changes in past evaporation and aridity.