PP23A-2274
East China Sea δ18O Record Detects Millennial-Scale Changes in the East Asian Summer Monsoon

Tuesday, 15 December 2015
Poster Hall (Moscone South)
Emma Gleeman1, Steven C Clemens2, Allison E Lawman1, Yoshimi Kubota3, Ann E Holbourn4, April Martin1 and Clemens Laboratory, (1)Brown University, Providence, RI, United States, (2)Brown University, Geological Sciences, Providence, RI, United States, (3)National Museum of Nature and Science, Ibaraki, Japan, (4)University of Kiel, Kiel, Germany
Abstract:
The East Asian Summer Monsoon (EASM) brings heavy summer rainfall to some of Asia’s most densely-populated areas, impacting agricultural production and water resources. Sediment cores were recovered from International Ocean Drilling Program Site U1429 in the East China Sea (31° 37.04’ N, 128° 59.50’ E, 732 mbsl). This location receives runoff from the Yangtze River, which serves as a major drainage system for monsoon-induced precipitation. Hence, the δ18O record of planktonic foraminifera at Site U1429 reflects changes in regional, monsoon-driven salinity. The top 100 meters of core at Site U1429 were sampled at a preliminary resolution of 15 cm and processed to isolate the planktonic foraminifer Globigerinoides ruber for δ18O mass spectrometry analyses. Abrupt, millennial-scale regional climate variability in the EASM and its linkage to orbital forcings have been reconstructed using stratigraphic analysis of δ18O. The sub-orbital scale structure of the δ18O record over the past 400 kyr matches the structures of both the composite speleothem δ18O from eastern China (Sanbao and Hulu caves) and the planktonic δ18O record from northern South China Sea Site 1146. The similarities between these δ18O records indicate a strong regional response to monsoon forcing. Removal of the temperature component of the δ18O signal by using Mg/Ca (G. ruber) paleothermometry will provide a record of changes in the δ18O composition of seawater in response to Yangtze River runoff.