Fingerprint of Climate Change on Southern Ocean Carbon Storage

• Published in: Global biogeochemical cycles 2023-04, Vol.37 (4), p.n/a
• Main Authors: Wright, R. M., Le Quéré, C., Mayot, N., Olsen, A., Bakker, D. C. E.
• Format: Article
• Language: English
• Subjects: Anthropogenic factors; Carbon; Carbon capture and storage; Carbon dioxide; Carbon dioxide atmospheric concentrations; Carbon sequestration; carbon storage; Climate change; Climate effects; Climate variability; Climatology; Deep water; Dissolved inorganic carbon; Fingerprints; Ocean basins; Ocean circulation; Oceans; Southern Ocean; Subduction; Transport; Uptake; Upwelling; Variability; Winds
• ISSN: 0886-6236; 1944-9224
• DOI: 10.1029/2022GB007596

The Southern Ocean plays a critical role in the uptake, transport, and storage of carbon by the global oceans. It is the ocean's largest sink of CO2, yet it is also among the regions with the lowest storage of anthropogenic carbon. This behavior results from a unique combination of high winds driving the upwelling of deep waters and the subduction and northward transport of surface carbon. Here we isolate the direct effect of increasing anthropogenic CO2 in the atmosphere from the indirect effect of climate variability and climate change on the reorganization of carbon in the Southern Ocean interior using a combination of modeling and observations. We show that the effect of climate variability and climate change on the storage of carbon in the Southern Ocean is nearly as large as the effect of anthropogenic CO2 during the period 1998–2018 compared with the climatology around the year 1995. We identify a distinct climate fingerprint in dissolved inorganic carbon (DIC), with elevated DIC concentration in the ocean at 300–600 m that reinforces the anthropogenic CO2 signal, and reduced DIC concentration in the ocean around 2,000 m that offsets the anthropogenic CO2 signal. The fingerprint is strongest at lower latitudes (30°–55°S). This fingerprint could serve to monitor the highly uncertain evolution of carbon within this critical ocean basin, and better identify its drivers. Key Points The effect of decadal climate variability on dissolved inorganic carbon (DIC) in the Southern Ocean is nearly as large as that of atmospheric CO2 Climatic drivers cause a distinct fingerprint on the change in DIC concentration in the Southern Ocean interior This fingerprint could serve to detect future trends in Southern Ocean carbon storage