Marine Sediments: A Reservoir for Black Carbon and their Use as Spatial and Temporal Records of Combustion

Summary

Black carbon (BC) found in ocean sediments provides regional and global information regarding biomass burning activities and transport mechanisms. BC fluxes to surface sediments, largely from the Pacific Ocean, range between 0.002–3.6 μg BC cm^-2 yr^-1 for deep sea sediments and 26–354 μg BC cm^-2 yr^-1 for continental margin sediments. The BC flux may be a function of the magnitude of biomass burning, the distance to the source region, and riverine and eolian transport mechanisms.

This manuscript presents some initial calculations of the global BC cycle. Using BC sediment flux data, we calculate global BC deposition to sediments in the deep ocean and continental margins, and compare these values to atmospheric deposition of BC to the global open and coastal ocean surface based on atmospheric BC concentration fields. About 10.4 Tg BC yr^-1 are deposited in ocean sediments, largely in the coastal ocean. BC deposition to the ocean surface is much more homogeneous throughout the ocean, accounting for deposition of 6.9 Tg BC yr^-1. We hypothesize that rivers may transport 12.2 Tg BC yr^-1 to the ocean and that these particulates are largely deposited in coastal ocean sediments. The manuscript discusses gaps in our knowledge of sedimentary BC and suggests future research initiatives that might further understanding of the global cycle and temporal distribution in ocean sediments of this product of biomass burning.