2:00 PM - 2:20 PM
[MIS01-02] Precession-band variance missing from East Asian monsoon runoff
Keywords:East Asian Monsoon, speleothem oxygen isotopes, seawater oxygen isotopes, East China Sea, Paleoclimate, greenhouse gas
We address this difference by attempting to replicate the YRV speleothem δ18O record at offshore Site U1429 in the East Chain Sea (ECS), drilled during IODP Expedition 346 (Tada et al., 10.2204/iodp.proc.346.101.2015). We utilize the same proxy system, δ18O of CaCO3, but recorded in surface-dwelling planktonic foraminifera (Foram δ18O). Foram δ18O replicates the precession-band and millennial-scale structure in YRV speleothem δ18O to a very high degree. We next quantitatively remove the effects of local surface temperature and global source-water δ18O to reconstruct local seawater δ18O, a record that responds primarily to dilution by local precipitation and runoff. Unlike speleothem δ18O, dominated almost exclusively by precession-band (23-kyr) variance, local seawater δ18O is dominated by eccentricity (100-kyr), obliquity (41-kyr), and heterodyne variance, with almost no precession-scale variance. The spectral structure of this record closely matches the spectral structure of global ice volume and greenhouse gasses, indicating that the EAM is more sensitive to high latitude ice sheet and greenhouse gas forcing than to direct insolation forcing.