Biogenic and terrestrial sediment records of the last two glacial cycles from offshore southeastern Papua New Guinea

The Western Pacific Warm Pool (WPWP) plays an important role in the global climate system. Here we present the last 180kyr carbonate, total organic carbon (TOC), terrestrial sediment component, 232Th activity and the C37 alkenones variations of millennial to orbital scales, based on a core MD052928 retrieved from offshore southeastern Papua New Guinea. We applied 230Th-normalized methods to estimate the total sedimentary fluxes which indicate higher fluxes in glacial stages. Terrestrial sediment component, flux and 232Th activity all indicate higher values in glacial stages and have the similar pattern to the total flux. This glacial-interglacial pattern may be attributed to more expanded continental shelves resulted from sea level changes, and/or higher fluvial input in the glacials. The high-frequency component of the variability of total flux and 232Th activity during the glacial stages may indicate rapid changes in the level of fluvial input in response to the intensity or duration changes of precipitation. TOC content and flux, and terrestrial sediment component show higher values but much reduced variability in glacial stages. The marine productivity proxy C37 alkenones content and flux variations are similar to TOC that indicates TOC could be contributed by marine productivity and terrestrial organic matter. In contrast, carbonate content and flux indicate high frequency variability and higher values in interglacials, and show clear variations on orbital bands. The maximum 232Th activity lags slightly Sanbo-Hulu’s δ18O maximum at the precession band, which indicates that the precipitation of south WPWP is out of phase with that of the East Asian monsoon. In addition, the carbonate flux is anti-phase with 232Th activity that may indicate marine productivity resulting from stronger SE trade is also linked to the Monsoon. Our results suggest the climate of south WPWP could be connected to the East Asian monsoon system through the migration of the Intertropical Convergence Zone.