Earth, Environmental, and Planetary Sciences, Brown University, Providence, 02912, RI, USA.
Institute of Geosciences, Christian-Albrechts-University, 24118, Kiel, Germany.
Nat Commun. 2018 Aug 22;9(1):3364. doi: 10.1038/s41467-018-05814-0.
Speleothem CaCO δO is a commonly employed paleomonsoon proxy. However, inferring local rainfall amount from speleothem δO can be complicated due to changing source water δO, temperature effects, and rainout over the moisture transport path. These complications are addressed using δO of planktonic foraminiferal CaCO, offshore from the Yangtze River Valley (YRV). The advantage is that the effects of global seawater δO and local temperature changes can be quantitatively removed, yielding a record of local seawater δO, a proxy that responds primarily to dilution by local precipitation and runoff. Whereas YRV speleothem δO is dominated by precession-band (23 ky) cyclicity, local seawater δO 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.
石笋 CaCOδO 是常用的古季风代用指标。然而，由于源水 δO 的变化、温度效应以及在水汽传输路径上的雨蚀，从石笋 δO 推断当地降雨量可能会变得复杂。这些问题可以通过长江流域（YRV）以外的浮游有孔虫碳酸钙的 δO 来解决。其优势在于可以定量去除全球海水 δO 和当地温度变化的影响，从而获得当地海水 δO 的记录，该指标主要响应于当地降水和径流入海的稀释。虽然 YRV 石笋 δO 主要受岁差带（23ky）的周期性控制，但当地海水 δO 主要受偏心率（100ky）和倾斜（41ky）的影响，几乎没有岁差尺度的变化。这些与 YRV 以外记录一致的结果表明，东亚季风降雨对温室气体和高纬度冰盖的驱动作用比直接太阳辐射的驱动作用更为敏感。
