Seasonality of precipitation recorded in a modern (1907-2008) annually laminated stalagmite from central China

Seasonality of precipitation in the Asian monsoon region has significant impacts on social and economic development. Here, we analyzed a seasonally resolved delta O-18 series of an annually laminated stalagmite from Xianglong Cave to assess its potential as a proxy for seasonal precipitation. The delta O-18 values reveal fabric-correlated annual cycles, with lower delta O-18 values occurring in the white porous layer (WPL) during summer monsoon (SM) season, whereas higher values occurring in the dark compacted layer (DCL) during non-summer monsoon (NSM) season. We calculated the seasonal amplitude of delta O-18 (Delta O-18) using the highest value minus the lowest value in an annual cycle. Comparisons suggest that the A Delta O-18 series can record precipitation seasonality, with lower Delta O-18 values corresponding to increased SM/NSM rainfall ratios and higher values corresponding to reduced SM/NSM rainfall ratios. Our reconstruction suggests increased precipitation seasonality contrast (i.e., increasing SM/NSM rainfall ratio with more SM rainfall and/or less NSM rainfall) during 1914-1919, 1935-1942, 1958-1962, 1979-1985, and 1999-2005 (A.D.), with a probably 27-year cycle. The seasonality of precipitation in central China correlates well with the Pacific Decadal Oscillation (PDO) on a decadal scale. Increased SM/NSM rainfall ratio was observed during the warm phase of PDO, and decreased SM/NSM rainfall ratio was observed during the cold phase of PDO