Hydroclimatic changes in China and surroundings during the Medieval Climate Anomaly and Little Ice Age: spatial patterns and possible mechanisms

摘要

Investigating hydroclimatic changes during key periods such as the Medieval Climate Anomaly (MCA, 1000-1300 AD) and the Little Ice Age (LIA, 1400-1900 AD) is of fundamental importance for quantifying the responses of precipitation to greenhouse gas-induced warming on regional and global scales. This study synthesizes the most up-to-date and comprehensive proxy moisture/precipitation records during the past 1000 years in China and surroundings. The proxy data collected include 34 records from arid central Asia (ACA) and 37 records from monsoonal Asia. Our results demonstrate a pattern of generally coherent regional moisture variations during the MCA and LIA. In mid-latitude Asia north of 30 degrees N, monsoonal northern China (North China and Northeast China) was generally wetter, while ACA (Northwest China and Central Asia) was generally drier during the MCA than in the LIA (a West-East mode). The boundary between wetter northern China and drier ACA was roughly consistent with the modern summer monsoon boundary. In monsoonal China to the east of 105 degrees E, the northern part was generally wetter, while the southern part was generally drier during the MCA than in the LIA (a North-South mode), with a boundary roughly along the Huai River at about 34 degrees N. These spatial patterns of moisture/precipitation variations are also identified by instrumental data during the past 50 years.