中文摘要：

理论分析表明,海水磷浓度控制了海洋自生磷沉积和热液磷沉积通量,并以此调节长尺度海洋磷循环的动态平衡.运用质量平衡原理,研究恢复了控制晚新生代海洋磷循环的各种通量,并据此模拟出海水磷浓度的演化.海水磷浓度演化与碳同位素分馏记录的浮游光合生物生长速度的变化一致,揭示在长时间尺度上,浮游光合生物的生长受海水磷含量控制.1500万年以来,大陆风化磷通量急剧增加,致使海洋磷浓度和磷沉积通量增加.海洋磷浓度增加促进了海洋生物生产力,导致海洋大气中生物气溶胶浓度升高,最终通过气溶胶的直接和间接辐射效应驱动晚新生代全球变冷.

英文摘要：

The long-term marine productivity is believed to be controlled by seawater phosphate availability. However, available proxies for seawater phosphate are rare and largely unreliable partly because phosphorus has only one natural isotope. Here we reconstruct the seawater phosphate concentration using a modeling approach. Theoretical analyses show that the authigenic and hydrothermal deposition of phosphorus from ocean is control by seawater phosphate concentration. The basic modeling idea is that it is the phosphate concentration that controls the authigenic and hydrothermal sink fluxes of phosphorus from seawater,which helps maintain the dynamic equilibrium of the long-term oceanic marine phosphate cycle. Thus, the model idea enable calculating the seawater phosphate concentration from the authigenic and hydrothermal sink fluxes of phosphate in world oceans, which could be reconstructed by subtracting the phosphate out fluxes of organic burial from the weathering influxes. Our previous works has already reconstructed the relative intensities of Cenozoic organic burial and continental weathering, both silicate and carbonate/sedimentary rocks, based on an inverse mass balance model using the marine carbon, strontium and osmium isotopic records（ Li G, Ji J, Chen J and Kemp D B,2009. Evolution of the Cenozoic carbon cycle： The roles of tectonics and CO2 fertilization. Global Biogeochemical Cycles, 23： GB1009, doi： 10. 1029/ 2008GB003220）. This work assigns the phosphate fluxes associated with organic burial and rock weathering. The modeled seawater phosphate concentration show dramatic increasing trend since 15Ma due to the increasing phosphate input from the weathering of continental rocks. The increasing phosphate concentration is in phase with the increasing growth rate of phytoplankton as recorded in the degree of carbon isotopic fractionation, which agree the general idea of the long-term control of seawater phosphate concentration on growth of marine phytoplankton. Increasing researches indicate that t