NOAA/WDS Paleoclimatology - East China Sea, offshore Yangtze River Valley d18O, d13C, and Mg/Ca Data and SST Reconstruction over the last 400,000 years

Speleothem CaCO3 d18O is a commonly employed paleomonsoon proxy. However, inferring local rainfall amount from speleothem d18O can be complicated due to changing source water d18O, temperature effects, and rainout over the moisture transport path. These complications are addressed using d18O of planktonic foraminiferal CaCO3, offshore from the Yangtze River Valley (YRV). The advantage is that the effects of global seawater d18O and local temperature changes can be quantitatively removed, yielding a record of local seawater d18O, a proxy that responds primarily to dilution by local precipitation and runoff. Whereas YRV speleothem d18O is dominated by precession-band (23-ky) cyclicity, local seawater d18O is dominated by eccentricity (100-ky) and obliquity (41-ky) cycles, with almost no precession-scale variance. These results, consistent with records outside the YRV, suggest that East Asian monsoon rainfall is more sensitive to greenhouse gas and high latitude ice sheet forcing than to direct insolation forcing.