Satellite derived estimates of global export flux composition and attenuation in the mesopelagic

Quantifying the ecosystem dynamics that transform carbon from the surface ocean into the twilight zone is critical for evaluating the role of the ocean in the global carbon cycle. Yet, these processes remain largely anonymous in current Earth system models. Here we build on a recent satellite based approach to quantify global sinking carbon flux from the surface ocean and link phytoplankton functional types partitioned by both size and composition into the satellite-based food web modeling to test the ballast hypothesis. A simple food web model that uses chlorophyll and the particle size distribution from SeaWIFS is modified with estimates of coccolithophore and diatom chl obtained from the SCIAMACHY satellite to trace the composition of carbon from the base of the euphotic zone into the mesopelagic. Deep sediment trap data from the updated Honjo et al. [2008] dataset are used to used to constrain the vertical fluxes of organic carbon, carbonate and opal to the deep ocean. Estimates of remineralization length scales from this method are consistent with previous findings. We use these results to model the roles of ballasting in determining composition-specific remineralization length scales. This synthesis of observations and models offers a first step towards quantifying the major components of export flux in the mesopelagic from remotely sensible observations.