Abstract
Asian summer monsoon (ASM) variability significantly affects hydro-climate, and thus socio-economics, in the East Asian region, where nearly one-third of the global population resides. Over the last two decades, speleothem δ18O records from China have been utilized to reconstruct ASM variability and its underlying forcing mechanisms on orbital to seasonal timescales. Here, we use the Speleothem Isotopes Synthesis and Analysis database (SISAL_v1) to present an overview of hydro-climate variability related to the ASM during three periods: the late Pleistocene, the Holocene, and the last two millennia. We highlight the possible global teleconnections and forcing mechanisms of the ASM on different timescales. The longest composite stalagmite δ18O record over the past 640 kyr BP from the region demonstrates that ASM variability on orbital timescales is dominated by the 23 kyr precessional cycles, which are in phase with Northern Hemisphere summer insolation (NHSI). During the last glacial, millennial changes in the intensity of the ASM appear to be controlled by North Atlantic climate and oceanic feedbacks. During the Holocene, changes in ASM intensity were primarily controlled by NHSI. However, the spatio-temporal distribution of monsoon rain belts may vary with changes in ASM intensity on decadal to millennial timescales.
Highlights
The Asian summer monsoon (ASM) transports heat and moisture during boreal summer (JJA)across the Indian Ocean and the tropical western Pacific into the Indian subcontinent and southeasternAsia, extending as far as northeast China and Japan [1]
There is a strong correlation between speleothem δ18 O series in the East Asian summer monsoon (EASM) and Indian summer monsoon (ISM) regions, but these data contrast with some other Chinese rainfall records reconstructed by loess and lake sediments [181,182,188]
China has witnessed a rapid increase in the number of speleothem studies over the last 20 years, with more than 100 speleothem records from ~80 caves published in ~300 papers
Summary
The Asian summer monsoon (ASM) transports heat and moisture during boreal summer (JJA). The ASM system includes two interacting subsystems: the East Asian summer monsoon (EASM) and the Indian summer monsoon (ISM). China is influenced by both the EASM and ISM and, it is essential to study monsoon variability on various timescales to understand their global teleconnections, underlying forcing mechanisms, and, in turn, improve our ability to predict long-term trends of hydroclimatic change. Over the past two decades, a large number of high-resolution speleothem δ18 O records from China have been used to characterize ASM variability and its underlying mechanisms across the late Quaternary at different timescales [5,8,9,10,11,12,13,14,15]. Because the interpretation of Chinese δ13 C records is underdeveloped due to its complexity, we focused this review on available δ18 O records
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