Description:
The regional dry-wet variation in the past ~2000 years is important for understanding the impact and driven forces of climate changes in the present and future, especially in arid areas. Sediment is one of the most useful achieves recording climate changes in such a time period, and selection and validation of qualified dry-wet proxies is the key approach for this research. However, such research still faces a challenge due to the limited acknowledge of physiochemical implications of the previous proxies in a specific lake, and the difficulties to discriminate dry-wet from warm-cold signals. In this work, a sediment core collected from Keluke Lake, Qaidam Basin was analyzed for iodine and uranium concentrations, to explore their potential as a dry-wet proxy in the arid regions and reconstruct the dry-wet changes during the past ~2200 years. The significant correlation between iodine and uranium concentrations (r=0.62, P<0.001) was observed, and four peak events of synchronously changed iodine and uranium concentrations occurred in AD 493-543, AD 740-1104, AD 1448-1538 and AD 1900-1914, respectively. This indicated a similar physiochemical deposition mode of the two elements from the catchment and lake water to sediments. During drier periods, the amounts of iodine and uranium leached from catchment soils increased due to the vegetation succession from the Artemisia-dominated steppe to the Chenopodiaceae-dominated desert, and the simultaneously increased suspended matter concentrations and/or organic content in lake water facilitated the formation of four peak events of iodine and uranium concentrations. The recorded four dry events coincide with the reported climatic changes in other lake sediments, ice core and aeolian sediments, and also correspond well with the society evolution in this area, including the establishment of Tuyuhun Kingdom (AD 313-663), Tubo Empire (AD 618-842), Mongolian tribes (AD 1495-1591, and the Han population immigration driven by a severe drought disaster in 1876-1879