Hydroclimate variability over the past 4730 years based on multi-proxy stalagmite records from southwest China

Abstract

Southwest China has experienced a series of record-breaking droughts over the last two decades, threatening regional ecosystems and exerting socioeconomic effects. Recent studies have focused on the drivers of specific drought events that seasonally vary in occurrence and duration, and a better understanding of regional paleo-records may be key to understanding their underlying mechanisms. Here, we present records of dry and wet alterations from 4730 yr B.P. based on multi-proxy stalagmite records. In particular, we report δ13C records at a five-year-resolution, and trace element (Mg, Sr, and Ba) to Ca ratios at a 25-year-resolution for stalagmite HD12 from Dark Cave, southwest China. Statistically significant correlations between δ13C and Mg/Ca suggest that they are controlled by a common factor, possibly related to local hydrological variations associated with the monsoon circulation. Long-term trends in the Sr/Ca and Ba/Ca ratios may be related to temperature- and/or precipitation-controlled growth rates. The first principal component (multi-proxy PC1) of δ13C and Mg/Ca can be used as the hydrological index in southwest China, indicating high-frequency oscillations on the millennial to multidecadal scales, with four prominent dry periods at 4255 ± 21 to 3430 ± 11, 2605 ± 12 to 2105 ± 9, 1755 ± 11 to 1255 ± 13, and 705 ± 8 to 405 ± 7 yr B.P. This is in general agreement with the monsoon index reconstructed from the detrended and z-scored cave δ18O PC1 in southwest China, indicating the sensitivity of regional hydrological response to monsoon intensity. The dry conditions of southwest China on the millennial-centennial scale may be related to solar forcing and the North Atlantic Oscillation owing to their influence on the strength and position of the westerlies and the Intertropical Convergence Zone. Additionally, the El Niño Southern Oscillation could also affect water vapor transport to southwest China by influencing the strength and position of the Walker circulation and Western Pacific Subtropical High. Moreover, the dry periods of southwest China over the past 4730 years are closely related to the warming of the sea surface temperature of the tropical warm pool on multidecadal scales. Such warming may be detrimental to the transport of water vapor from the North Western Pacific and Indian Ocean to southwest China, resulting in a dry regional environment.