Late Holocene climate variation on the northern Tibetan Plateau inferred from Lake Ayakum

Abstract

Understanding late Holocene climate variation on the northern Tibetan Plateau is essential for understanding regional climate dynamics, especially the potential response to mid-latitude westerlies. A continuous lacustrine sediment record covering the past 1500 years was recovered from Lake Ayakum on the northern margin of the Tibetan Plateau, in which a typical cold-phase mineral (mirabilite) was detected. Assisted by the simulation results in the Pitzer model, the preservation of mirabilite in the sediment core as well as its relative proportion was interpreted in terms of past temperature variations, in which a high mirabilite content corresponded to a relatively cold environment. Grain size analysis and subsequent end-member modeling results revealed potential correlations with regional moisture conditions, that more coarse materials were transported by increased river discharge under relatively wet conditions. The results showed that cold and humid conditions dominated the Dark Age Cold Period and Little Ice Age, while warm and dry conditions dominated the Medieval Warm Period. Following the increase in regional temperature, more coarse materials were deposited during the last 200 years owing to probable increased fluvial transport supplied by glacier meltwater. The overall temperature and moisture variations were broadly consistent with records from western China and central Asia, indicating that the northern Tibetan Plateau was predominately influenced by the mid-latitude westerlies during the late Holocene. In addition, the temperature change showed a close correlation with solar irradiance, pointing to a potential response to solar activity. On the other hand, the moisture change responded sensitively to the North Atlantic Oscillation and the migration of mid-latitude westerlies.