Variation in the Asian monsoon intensity and dry–wet conditions since the Little Ice Age in central China revealed by an aragonite stalagmite
- 1Key Laboratory of Karst Dynamics, MLR and Guangxi, Guilin, Guangxi 541004, China
- 2School of Geographical Sciences, Southwest University, Chongqing 400715, China
- 3Institute of Karst Geology, CAGS, Guilin, Guangxi 541004, China
- 4Department of Geosciences, National Taiwan University, Taipei 10617, Taiwan
- 5Institute of Global Environmental Change, Xi'an Jiaotong University, Xi'an 710049, China
- 6Department of Earth Sciences, University of Minnesota, Minneapolis 55455, USA
- 7Department of Environmental and Resource Sciences, LiuPanShui Normal University, Liupanshui 553004, China
- 8Department of Earth Sciences, National Taiwan Normal University, Taipei 11677, Taiwan
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 The comparison of the δ18O record with the local instrumental record and historical documents indicates that (1) the stalagmite δ18O record reveals variations in the summer monsoon intensity and dry–wet conditions in the Wuling Mountain area.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.