Strong Transport of Anthropogenic Carbon from the Antarctic Shelf to Deep Southern Ocean

Abstract Flows of dense shelf water are an efficient mechanism for pumping CO2 to deep ocean along the continental shelf-slope, particularly in the Antarctic Bottom Water (AABW) formation area and its adjacent waters where most of the global bottom water is formed. The global carbon uptake from the atmosphere is estimated to be 200 teragrams carbon per year (Tg C yr-1). However, the contribution from the Antarctic coastal regions to the global carbon budget remains highly uncertain. Here, using an integrated observational dataset, we find that the export of anthropogenic CO2 from the Pan-Antarctic shelves to deep Southern Ocean is 45~86 Tg C yr-1, equivalent to 22~43% of the global coastal CO2 uptake, and much higher than previous estimates. The large carbon transport flux causes a decline in deep water pH of 0.0007 ± 0.0002 pH yr-1, far faster than that of any other open ocean deep waters (<0.0002 pH yr-1). Thus, CSP in the AABW formation area is an important pathway for anthropogenic carbon transport into the ocean interior.