Although temperature decreased in a similar trend in many regions around the word during the Little Ice Age (LIA), the reconstructed humidity is remarkably different from region to region. The precipitation history during the LIA is poorly understood as compared to the temperature history in tropical South China. In this study, a sediment core with a length of 117.5 cm was recovered in the central part of Huguangyan Lake in tropical South China. Total organic carbon (TOC), total nitrogen (TN), inorganic carbon (IC) and non-residual strontium (Sr) were analyzed at approximately 1 cm intervals to study the regional precipitation changes during the LIA. Generally, Sr-containing minerals are sensitive to chemical weathering which is dominated by the precipitation in tropical South China. Thus the non-residual Sr in Huguangyan sediments can be used as an indicator of precipitation changes, which is also verified by the downcore variations of TOC, TN and IC in Huguangyan Lake. The non-residual Sr correlated positively with TOC and TN but negatively with IC in the sediment profile. TOC, TN, IC and the non-residual Sr jointly demonstrated a wet period from AD 1500 to 1750, which corresponds to the LIA. Coincidently, both the total solar irradiance (TSI) and Northern Hemisphere temperature have the lowest values between AD 1500 and 1750 over the past millennium. Therefore, the wet LIA in tropical South China was most likely caused by the low solar irradiation. During the LIA, the low solar irradiation likely resulted in the decrease of the Northern Hemisphere temperature, which weakened the intensity of the East Asian summer monsoon (EASM) and synchronously moved the north edge of the Asian summer monsoon southward, leading to an increase in the precipitation in tropical South China.
修改评论