Environmental change in the western Pacific during the late Quaternary - Deglaciation to Holocene

As a part of the Japanese IMAGES activity, a 33.65 in long core (MD982195) with very high sedimentation rate (ca. 80 cm kyr^-1) was retrieved from the northern part of the East China Sea, one of the largest marginal seas in the world. Stable isotope of oxygen and carbon in shells of planktonic foraminifera Globigerinoides ruber, sea surface temperature (SST) from alkenones (U^k′₃₇) in bulk sediment, Q-mode factor analysis of planktonic foraminiferal assemblage, pollen and spores assemblage, and biogenic and abiogenic components were analyzed in order to understand fluctuations in terrestrial and marine environments influenced by the East Asian Monsoon during the last 42 kyr. Besides the similaliry between the δ¹⁸O and alkenone SST curve, many light δ¹⁸O peaks, apparently corresponding to Dansgaard-Oeschger (D-O) cycles as observed in Greenland ice cores, were observed for the last 42 ka. We analysed G. ruber sensu stricto (s.s.), which represents shallower environments (lives in the upper water column) than G. ruber sensu lato (s.l.). The meandering of the westerlies during the cold and warm D-O cycles would have established an atmospheric tele-connection between East Asia and Greenland. Based upon contents of organic carbon, nitrogen and total amino acids, the estimated primary production was approximately constant during 42-15 ka, increased in 15-14 ka, and remained constant until 7 ka. Subsequently, primary production increased from 5 ka to the present. High sedimentation rate was attributed to high flux of terrestrial lithogenics, which were transported mainly from coastal lowlands and not from inland of China by wind. The environment in the marginal seas in the western Pacific was much affected by sea level change. D-O cycles were also reported from the IMAGES cores collected from the equatorial western Pacific. This area would have played an important role in the global climatic change and atmospheric concentration Of CO₂, N₂O and CH₄ through the changes in the Walker circulation, which is closely related to ENSO (ENSO: El Niño/ Southern Oscillation).