The ballast effect of riverine lithogenic matter and its influence on POC fluxes in the ocean
Shasha Li 1,2, Shanlin Wang 1,2, *
1. College of Ocean and Earth Sciences, Xiamen University, China
2. State Key Laboratory of Marine Environmental Science (Xiamen University)
The export of particulate organic carbon (POC) plays a key role in the ocean carbon cycle. The downward transport of POC is drived by ballast minerals include calcium carbonate, biogenic silicon and lithogenic matter. However, in previous assessments of global POC flux using models, studies of lithogenic matter that produce ballast effect mainly focus on the aeolian dust and its effects on the regions of strong atmospheric dust deposition, lack the consideration of riverine lithogenic matter. We therefore compiled the global river-borne sediment input data, generated a simplified riverine lithogenic matter forcing field, and applied to the Community Earth System Model simulation to understand the influence of riverine lithogenic ballast on POC flux and other biogeochemical parameters. Results show that annual POC export of 100m increases obviously at river points after considering the riverine lithogenic matter, accompanied by higher carbon sequestration under 1000m. The resulting reduced organic carbon remineralization further causes a decrease of phytoplankton biomass in near-surface throughout the year but an increase in subsurface especially in summer. The addition of riverine lithogenic matter, however, exerts modest negative effect on annual POC export of global marginal seas. Even so, POC flux of 1000m enhances about 15% in global marginal seas compared to control scenario when we assess one extreme scenario with high concentration of riverine lithogenic matter input and long transmission distance. In adition, POC flux decreases in the tropical eastern pacific and subpolar oceans and increases in the subtropical oligotrophic gyres in terms of global pattern.
Keywords：POC, ballast effect, riverine lithogenic matter
