Decadal‐ to Centennial‐Scale East Asian Summer Monsoon Variability Over the Past Millennium: An Oceanic Perspective

Abstract

The East Asian summer monsoon (EASM) is a key component of the Asian Monsoon system affecting regional precipitation in East Asia and thus human culture, society, and development. Despite this, decadal‐ to centennial‐scale EASM dynamics remain poorly understood over the last millennium. Here we used high‐resolution benthic microfossil proxies to reconstruct EASM variability for the last 1,000 years from a brackish lake in South Korea. We compared this EASM record with Asian Monsoon proxy records from East China (i.e., continental proxy) and East Asian coasts (i.e., oceanic setting), and identified four pervasive EASM strengthening events at 1250, 1450, 1550, and 1900 CE and their deviation, likely related to land‐ocean temperature gradients. Our results indicate that data from the oceanic setting under the direct influence of the Pacific High are important in understanding the EASM dynamics over the last millennium. It is also noteworthy that EASM variability shows striking similarity to changes in the Atlantic meridional overturning circulation, implying the causal relationship.

Asynchronous multi-decadal time-scale series of biotic and abiotic responses to precipitation during the last 1300 years

“…2 d, 3 , and Supplementary Figure S3 ). With Butterworth low-pass filtering, our data were comparable to those for Lakes Songji 18 and Hwajinpo 16 , with the exception of a few periods (e.g., 1150–990 CE in Fig. 2e and 1290–1190 CE in Fig.…”

“…DBL F., deciduous broadleaved forest.

Figure 2 Pollen-based quantitative annual precipitation (PqPann) and artificial neural networks (ANNs) Pann reconstruction from 650 to 1950 CE and their verification by comparison with the Korean proxy results of the relative sand contents (%) of KL-29 22 , oxygen isotopes (δ 18 O ‰ VPDB) of Baeg-nyeong Cave (BN-1) 9 , the foraminifera index 16 , old (Chukwooki; 1777–1910) and modern (1908–1995) rain gauge data 20 , 21 , and drought records from the annals of the Joseon Dynasty 8 . ( a ) PqPann (light gray line), old rain gauge data (green line), and frequency of droughts (black dotted line).

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Holocene EASM‐EAWM Relationship Across Different Timescales in CCSM3

“…It can be seen that, at millennial and shorter timescales, AMOC is always positively correlated with EASM (Figure 3, red line), but negatively correlated with EAWM (Figure 3, blue line). The positive relation between AMOC and EASM at decadal‐centennial timescales is also found in the benthic microfossil proxies over the last millennium (Cheung et al, 2018). At the orbital timescale, EASM becomes negatively correlated with AMOC (Figure 3), as shown clearly in the trend of the time series, which shows a strengthening trend in AMOC but a decreasing trend in EASM (Figure 2b).…”

Regional differences in summer monsoon precipitation variability reconstructed from multiple proxies in Asia during the past millennium

“…Comparing with the multidecadal ASM variation derived from stalagmite (Zhang et al, 2008) and high- resolution lake sediments (Cheung et al, 2018), the results show that there has been no fixed matching pattern between the dry/wet periods and the shift of the ASM regime. In the East Asian summer monsoon area, the wet period of 970-990 corresponded to strong ASM, but the other wet periods (i.e., 1330-1350, 1380-1430 and 1550-1580) corresponded to weak ASM.…”