Southern Ocean anthropogenic carbon sink constrained by sea surface salinity

• Published in: Science Advances
• Main Authors: Terhaar, Jens, Frölicher, Thomas L., Joos, Fortunat
• Format: Text
• Language: English
• Published: American Association for the Advancement of Science 2021
• Subjects: Research Articles; Southern Ocean
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8081370/; http://www.ncbi.nlm.nih.gov/pubmed/33910904; https://doi.org/10.1126/sciadv.abd5964

The ocean attenuates global warming by taking up about one quarter of global anthropogenic carbon emissions. Around 40% of this carbon sink is located in the Southern Ocean. However, Earth system models struggle to reproduce the Southern Ocean circulation and carbon fluxes. We identify a tight relationship across two multimodel ensembles between present-day sea surface salinity in the subtropical-polar frontal zone and the anthropogenic carbon sink in the Southern Ocean. Observations and model results constrain the cumulative Southern Ocean sink over 1850-2100 to 158 ± 6 petagrams of carbon under the low-emissions scenario Shared Socioeconomic Pathway 1-2.6 (SSP1-2.6) and to 279 ± 14 petagrams of carbon under the high-emissions scenario SSP5-8.5. The constrained anthropogenic carbon sink is 14 to 18% larger and 46 to 54% less uncertain than estimated by the unconstrained estimates. The identified constraint demonstrates the importance of the freshwater cycle for the Southern Ocean circulation and carbon cycle.