Palaeoproductivity evolution in the centre of the western Pacific warm pool during the last 250 ka

摘要

To reconstruct the palaeoproductivity evolution history of the centre of the western Pacific warm pool (WPWP) over the last 250 ka, multi-proxies were analysed in sediment core WP7 recovered from the Ontong-Java Plateau. Palaeoproductivity evolution at the centre of the WPWP during the last 250 ka is closely related to glacial-interglacial cycles and the insolation controlled by precession. The glacial higher primary productivity relative to the interglacial conditions could have resulted from both thermocline shoaling associated with persistent El Niňo-like conditions and the increased influx of dust resulting from intensified winter monsoon together with important changes in the thermocline. The minimum primary productivity values during the last three terminations could be resulted from deglacial thermocline deepening and intensified stratification associated with persistent La Ni?a-like conditions, and the concurrent Neogloboquadrina dutertrei δ~(13)C minimum events probably reflect the chemical signatures of Subantarctic Mode Water and Antarctic Intermediate Water. In addition, primary productivity values are also controlled by the thermocline variations resulting from El Ni?o/La Ni?a-Southern Oscillation processes responding to precession forcing, and lead the δ~(18)O by about 4 ka. The 33.1 ka, 19 ka and "half-precession" periods are prominent in the palaeoproductivity records.