Disappearance of Mountain Glaciers in East Asian Monsoon Region since Onset of the Last Glacial Period

Abstract

Discussing the development and shrinkage process of glaciers is of great significance for the in–depth comprehension of regional environmental evolution and predicting global changes. However, there is little understanding of the developmental and retreat processes of mountain glaciers during the Late Quaternary (150 ka) in the East Asian Monsoon region. Using the latest chronological glacial data from eastern China, Taiwan, the Russian Far East, and the Japanese islands of Hokkaido and Honshu, which are all regions impacted by the East Asian Monsoon, we screened reliable glacial age data. This study compiled and compared the age sequences of the different mountain glaciations (dating techniques included optically–stimulated luminescence (OSL), thermoluminescence (TL), electron spin resonance (ESR), U–series (U), cosmogenic nuclides (10Be/CRN), carbon–14 (14C) and potassium–argon (K–Ar), etc.). Based on the evolutionary features of the glaciations in these mountains, by comparison with the marine isotope stage (MIS) environment, the influence of monsoonal circulation patterns on the regional development of glaciers was analyzed. This study determined that Japanese mountain glacial stages since 150 ka are the most complete in the East Asian Monsoon region, having developed during MIS 6–1. Taiwanese mountain glaciers developed during MIS 4–1, but glacial stages in continental East Asia were relatively short, with glaciers first developing only during MIS 3b–1. The reason for this this phenomenon is that the tectonic uplift in different subregions was significantly different; on the other hand, it is also related to the difference of precipitation between land and sea in monsoon climate. By comparing the glacial glaciations in the East Asian Monsoon region with western China, we found that there were significant differences between the extent, onset time, and length of glacial periods. Since the Last Glacial Period, precipitation levels have become transitional and concentrated during the summer months, and temperatures have been continuously changing as a result of the many periodic changes in the East Asian Monsoon. From the Early Last Glacial Period (MIS 4) to the Middle Last Glacial Period (MIS 3b) to the Last Glacial Period (MIS 2/LGM–YD), climatic conditions increasingly restricted the development of glaciers; the regional environment continued to warm until glaciers completely disappeared during the Late Holocene.

Keywords

• East Asian Monsoon
• Last Glacial Period
• monsoon circulations
• mountain glaciation sequences