Phytoplankton biomarkers were analyzed using suspended particles collected from the northern South China Sea(SCS)during the summer cruise of2008,with the goal of understanding the algal community structure and biomass distribution pattern in the summer season.The results indicated that the distribution of algal biomarkers in surface water of SCS was impacted and constrained by the local hydrological settings:the high biological community generally appeared in Pearl River estuaries,southwestern off Taiwan island and southeastern off Hainan Island,while the relatively lower biomass was found in the deep basin and strait areas.Diatoms were the dominant phytoplankton species,which were followed by dinoflagellates.Coccolithophorid biomass gradually increased toward the open ocean.The present work indicated that the algal biomarkers effectively documented the variability of the phytoplankton biomass and community structure as well as their linkage with the oceanic dynamics in SCS during summer 2008.This research provided not only the foundation for the application of algal lipids in the modern ocean ecosystem,but also the basis for the reconstruction of the past oceanic algal community structures.
Forced by transient solar activities since 7 ka,the thermal structures of the Pacific upper water at boreal winter are featured by an enhanced response of 3-dimensional Western Pacific Warm Pool(WPWP) in an Earth system model of Intermediate Complexity at centennial scales.During solar maximum periods,the magnitude of surface ocean temperature variations is 30% larger in the western tropical Pacific than in the Ni o3 region,while at subsurface,it is 40% larger in the subtropical North Pacific than in the western Equatorial Pacific.They compromise stronger zonal and meridional thermal gradients in surface and subsurface Pacific respectively which are both linearly responded to solar forcing at centennial periods.The surface gradient is most sensitive at 208-year period while the subsurface gradient shows more significance at periods longer than 208-year.Also noteworthy are two differences:(1) the phase lags at these periods of surface gradient are slightly smaller than that of subsurface;(2) the 148-year and 102-year periods in surface gradient are lost in subsurface gradient.These modeled features preliminary confirm the centennial fluctuations of WPWP in paleo-proxies and a potential solar forcing during the Holocene.
To constrain short-term changes of climate and oceanography in the northern South China Sea(SCS)over interglacial marine isotope stage(MIS)5.5,we studied planktic and benthic 18O records of seven marine sediment cores with a time resolution of70–700 yr.Using 6–8 tie points the planktic records were tuned to the U/Th chronology of speleothem 18O records in China and Europe.The last occurrence of pink Globigerinoides ruber marks the top of Heinrich stadial 11(HS-11)near 128.4 ka.HS-11 matches a 2300-yr long positive 18O excursion by 1.5/0.8‰both in planktic and benthic 18O records.Hence half of the planktic 18O signal was linked to increased upwelling of18O-and12C-enriched deep waters in the southwestern SCS.The increase was possibly linked to a strengthened inflow of Pacific deep waters through the Bashi Strait,that form a boundary current along the northern slope of the SCS,building a major sediment drift.At its lower margin near 2300–2400 m water depth(w.d.)Parasound records reveal a belt of modern erosion.At the end of glacial termination 2,stratigraphic gaps deleted HS-11 in core MD05-2904 and subsequent peak MIS 5.5 at ODP Site 1144.Likewise hiatuses probably earmarked all preceding glacial terminations at Site 1144 back to 650 ka.Accordingly,boundary current erosion then shifted^300 m upslope to^2040–2060 m w.d.These vertical shifts imply a rise in boundary current buoyancy,that in turn may be linked to transient events of North Pacific deepwater formation similar to that traced in SCS and North Pacific paleoceanographic records over glacial termination 1.
