The 'Little Ice Age' recorded by sediment chemistry in Lake Erhai, southwest China

On the basis of concentrations of 21 major and minor elements in a well-dated sediment core from the deepwater part of Lake Erhai, principal component analysis (PCA) reveals three main factors controlling the inorganic chemical composition of lake sediments. These are physical erosion in the watershed (Component 1), autochthonous calcite precipitation in lake water (Component 2) and early diagenesis in sediments (Component 3). Variations of factor scores of Component 1 and Component 3 may reflect fluctuations in rainfall and temperature, respectively in the lake region. High factor scores of Component 3 correlate with low factor scores of Component 1 in sediments within the intervals AD 1340-1550 and AD 1890-1950, indicating two warm-dry episodes. Low factor scores of Component 3 correlate with high factor scores of Component 1 from AD 1550-1890, indicating a cold-wet climate corresponding to the 'Little Ice Age' in Europe. Our study provides a new approach to reconstructing palaeoclimate, and adds to a growing body of evidence for a widespread cooling during the 'Little Ice Age'. The alternation between warm-dry and cool-humid conditions possibly implies different climate change characteristics between the southwest monsoon zone and the southeast monsoon zone where the climate pattern is warm-humid and cool-dry.