Variation in the Asian monsoon intensity and dry–wet conditions since the Little Ice Age in central China revealed by an aragonite stalagmite

R. L. Edwards,H.-S. Mii,H.-C. Li,Y.-S. Lin,J.-J. Yin,Z.-Y. Zhao,J.-M. Qin,T.-Y. Li,W. Tang,D.-X. Yuan,H. Cheng

doi:10.5194/cp-10-1803-2014

R. L. Edwards, H.-S. Mii + Show 9 more

Open Access

https://doi.org/10.5194/cp-10-1803-2014

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Abstract

Abstract. This paper focuses on the climate variability in central China since AD 1300, involving: (1) a well-dated, 1.5-year resolution stalagmite δ18O record from Lianhua Cave, central China (2) links of the δ18O record with regional dry–wet conditions, monsoon intensity, and temperature over eastern China (3) correlations among drought events in the Lianhua record, solar irradiation, and ENSO (El Niño–Southern Oscillation) variation. We present a highly precise, 230Th / U-dated, 1.5-year resolution δ18O record of an aragonite stalagmite (LHD1) collected from Lianhua Cave in the Wuling Mountain area of central China. The comparison of the δ18O record with the local instrumental record and historical documents indicates that (1) the stalagmite δ18O record reveals variations in the summer monsoon intensity and dry–wet conditions in the Wuling Mountain area. (2) A stronger East Asian summer monsoon (EASM) enhances the tropical monsoon trough controlled by ITCZ (Intertropical Convergence Zone), which produces higher spring quarter rainfall and isotopically light monsoonal moisture in the central China. (3) The summer quarter/spring quarter rainfall ratio in central China can be a potential indicator of the EASM strength: a lower ratio corresponds to stronger EASM and higher spring rainfall. The ratio changed from <1 to >1 after 1950, reflecting that the summer quarter rainfall of the study area became dominant under stronger influence of the Northwestern Pacific High. Eastern China temperatures varied with the solar activity, showing higher temperatures under stronger solar irradiation, which produced stronger summer monsoons. During Maunder, Dalton and 1900 sunspot minima, more severe drought events occurred, indicating a weakening of the summer monsoon when solar activity decreased on decadal timescales. On an interannual timescale, dry conditions in the study area prevailed under El Niño conditions, which is also supported by the spectrum analysis. Hence, our record illustrates the linkage of Asian summer monsoon precipitation to solar irradiation and ENSO: wetter conditions in the study area under stronger summer monsoon during warm periods, and vice versa. During cold periods, the Walker Circulation will shift toward the central Pacific under El Niño conditions, resulting in a further weakening of Asian summer monsoons.

Highlights

The Little Ice Age (LIA; according to Matthes (1939) and Lamb (1977) from ∼ AD 1550 to 1850; hereafter all dates are AD) was the last drift-ice cycle (Bond et al, 2001) characterized by cold conditions (PAGE 2k Consortium, 2013)
We present a highly precise, 230Th / U-dated, 1.5-year resolution δ18O record of an aragonite stalagmite (LHD1) collected from Lianhua Cave in the Wuling Mountain area of central China
Our study indicates that variations of solar irradiation, air temperature and ENSO conditions are important forcing factors to influence the Asian monsoonal climates on decadal to centennial scales, whether speleothem records on such timescales are comparable remains the question

Summary

Introduction

The Little Ice Age (LIA; according to Matthes (1939) and Lamb (1977) from ∼ AD 1550 to 1850; hereafter all dates are AD) was the last drift-ice cycle (Bond et al, 2001) characterized by cold conditions (PAGE 2k Consortium, 2013). Several high-resolution and precisely dated speleothem records in the Asian monsoon region (i.e., Zhang et al, 2008; Tan et al, 2009; Burns et al, 2002; Hu et al, 2008; Li et al, 2011; Wan et al, 2011) reveal an excursion of the δ18O toward heavier values over the past several decades that was interpreted as a weak monsoon trend. The East Asian summer monsoon (EASM) index showed a general decrease trend since 1920 (IPCC, 2007; Wang et al, 2006). If both the cold conditions during the LIA and warm conditions during the Current Warm Period (CWP) resulted in weak EASM on decadal timescales, what are the driving forces for variability of the Asian summer monsoon? We probe the relationships among solar irradiation, ENSO, temperature and summer monsoon precipitation and, in turn, the influencing factors for summer monsoon precipitation in central China since 1300

Cave site and local climate conditions

Sample description

Comparison of the δ18O record with weather records

Solar radiation influence and teleconnection to ENSO

Findings

Comparison of speleothem records in the Asian monsoonal region

Conclusions