Dissolved organic carbon in the Ross Sea: Deep enrichment and export

Antarctica's continental shelves generate the densest waters in the world and are responsible for the formation of Antarctic Bottom Water (AABW), a water mass with the potential to sequester carbon in the deep ocean for millennia. One such form of marine carbon is dissolved organic carbon (DOC), the ocean's largest standing stock of reduced carbon. In this study, we quantify DOC enrichment in dense shelf waters (DSW) in the Ross Sea and assess the potential for DOC to be sequestered from Antarctic shelves into AABW. We find that Ross Sea DSW is enriched in DOC by ∼7 μmol kg−1 relative to the incoming source waters (initial conditions), which is primarily caused by vertical mixing. The total DOC excess in DSW suggests that 4.0 ± 0.6 Tg DOC yr−1 is exported off the shelf. However, this exported fraction does not appear to persist in newly formed AABW and is likely remineralized, sequestering this carbon as TCO2 in the deep ocean.