The Distribution Characteristics And Influence Mechanism Of The Suspended Particulate Matter In The North Of The Western Pacific Warm Pool

Western Pacific Warm Pool(WPWP)plays an important role in the energy transportation and material circulation in the earth system.The hydrological environment changes of the WPWP can affect the evolution of the ocean depositional systems and marine ecosystems.As an important carrier of the material transport and energy exchange in the ocean,the oceanic suspended particulate matter(SPM)is of great significance to reveal the process of oceanic sedimentation.Combined with analysis of hydrodynamics environment and SPM related parameters in the north of the WPWP,we detailedly reveal the distribution characteristic and composition characteristics of the SPM in the study area;explores the material source of the SPM in the study area;and summarize the influence mechanism of the oceanic SPM in the study area.During December 30,2014 to January 30,2015,several hydrological parameters and SPM related parameters in the water column shallower than 2000 m depth were obtained during the investigation onboard research vessel �Kexue�.The semi-quantitative elemental analysis of oceanic SPM were measured using the synchrotron radiation micro-beam X-ray fluorescence(SRXRF)analysis.Combined with the satellite altimeter observations and Argo profile data,this paper reveals the hydrodynamic environments characteristics,the distribution characteristics of SPM,the elemental composition of the SPM in the study area,and discusses the sources of the SPM and the influence mechanism of the SPM in the study area.(1)All stations showed strong �jump layers� of hydrological parameters in the upper water,here refers to waters shallower than 800 m,including the thermocline,halocline,pycnocline,and jump layer of the dissolved oxygen.The deep water,here refers to waters between 800 m and 2000 m,showed relative stable hydrodynamic environment.The WPWP effect,ocean current structure and mesoscale activities are the important influencing factors of the hydrodynamic environment characteristics.(2)Four SPM related parameters of the water column,including the SPM concentration,the total volume concentration,the median diameter and the in-situ fluorescence chlorophyll concentration,existed near hydrological jump layers.But the distribution characteristics of the SPM of the stations in the WPWP showed great difference from other stations out the WPWP,especially in the upper water.(3)The source of the SPM includes the external terrigenous material inputs and the internal organic components.Results from the profile distribution of the element associated to SPM and the principal component analysis showed that element Ca,Cu,Zn,Sr in the SPM can be used to represent the biogenic materials,which exhibited maxima near the subsurface chlorophyll maximum layer(SCML)and were mainly controlled by the biological activities.Elements Ti,Mn,Fe,Zr in the SPM can represent the terrigenous materials,which exhibited maxima in the euphotic layer and also showed peak values in the layer of 300 m at I-8 station in particular.(4)The hydrological structure of the upper water in the study area plays an important controlling role in the formation of the subsurface chlorophyll maximum(SCM).And the in situ phytoplankton bloom around the pycnocline can be largely attributable to the formation of the well-developed SCML in the studied system.The mesoscale eddies exerted significant controlling effects on the hydrological structure and chlorophyll distribution and further controlled the distribution of the biogenic material.In addition,the offshore core of the northward-flowing Mindanao Undercurrent(MUC)transports relative hypersaline subsurface water at density surfaces of 26.2-27.0 ??,which is rich in terrigenous particle materials,prior to the convergence that forms the eastward-flowing NEUC.