Assessing recent anthropogenic carbon dioxide and acidification in the Ross Sea, Antarctica

Over the past decade, the East Ross Sea has experienced a significant decline in sea ice, enabling direct observational studies of regional carbon dynamics. The accumulation rate of anthropogenic CO₂ in the East Ross Sea is up to six times higher than the long-term Industrial Era mean due to the inflow of seawater from the Amundsen Sea by accelerated glacial melting. In contrast, the West Ross Sea exhibited comparatively smaller changes. Measurements of dissolved inorganic carbon and stable carbon isotope indicate that, over the period 2011-2020, changes in δ¹³C (Suess effect) and anthropogenic CO₂ were 0.20 ± 0.06‰ and -5 ± 2 μmol kg^-1 in the West Ross Sea, and -0.15 ± 0.01‰ and 9 ± 1 μmol kg^-1 in the East Ross Sea. These findings suggest rapid acidification in the East Ross Sea, with aragonite undersaturation likely to occur by the mid-2030s, accompanied by an expected pH decrease of ∼0.2 units by the end of the century.