Hydrological changes in Shuangchi Lake, Hainan Island, tropical China, during the Little Ice Age

Hydrological changes in East Asia during the last millennium have been addressed by numerous earlier studies, but spatial characteristics and dynamics in precipitation variations during the Little Ice Age (LIA) remain unclear, perhaps especially due to the sparse coverage of high-resolution hydrological records from tropical and sub-tropical regions in East Asia. In this study, a sediment core was obtained from Shuangchi Lake in northern Hainan Island, tropical China, of which geochemical proxies including the ratios of Rb/Sr, Rb/K, Zr/Rb and Si/Ti were analyzed using an X-ray fluorescence (XRF) core scanner. Meanwhile, the grain size distribution of sediments was also determined. The results show that the Rb/Sr and Rb/K ratios decreased significantly during the LIA, whilst the Zr/Rb and Si/Ti ratios increased along with higher median grain size. The changes of these proxies likely suggest that precipitation was enhanced during the LIA in this region, and this was consistent with other hydrological records from tropical southern China. The synthesis of hydrological records from East Asia and the tropical Pacific suggest that the co-existence of a contracted Intertropical Convergence Zone (ITCZ) and strengthened Pacific Walker circulation (PWC) could contribute synchronously to the increased precipitation in the tropical region of southern China during the LIA.