Fig. 4: Schematics of the dissolved black carbon (DBC) cycle in the ocean, with emphasis on the Pacific Ocean.

The pool sizes of surface DBC, mesopelagic DBC and abyssal DBC were estimated from the dissolved organic carbon (DOC) pool size⁴³ and the DBC contribution to DOC³¹ (Table 1). The riverine input flux was obtained from Jones et al.¹⁹. The atmospheric deposition flux is the dry deposition flux of water-soluble black carbon (BC) in aerosols⁵³. The photodegradation flux was obtained from Stubbins et al.²². The flux of sorption onto sinking particles was estimated in this study (Table 1). The units of the pool sizes and fluxes are PgC and PgC year⁻¹, respectively.