Transport of Anthropogenic Carbon From the Antarctic Shelf to Deep Southern Ocean Triggers Acidification

• Published in: Global Biogeochemical Cycles
• Main Authors: Zhang, Shuang, Wu, Yingxu, Cai, Wei‐Jun, Cai, Wenju, Feely, Richard A., Wang, Zhaomin, Tanhua, Toste, Wang, Yanmin, Liu, Chengyan, Li, Xichen, Yang, Qinghua, Ding, Minghu, Xu, Zhongsheng, Kerr, Rodrigo, Luo, Yiming, Cheng, Xiao, Chen, Liqi, Qi, Di
• Format: Article in Journal/Newspaper
• Language: English
• Published: AGU (American Geophysical Union) 2023
• Subjects: Antarctic; Southern Ocean; The Antarctic; Antarc*; Antarctica
• Online Access: https://oceanrep.geomar.de/id/eprint/59722/; https://doi.org/10.1029/2023GB007921

Flow of dense shelf water provide an efficient mechanism for pumping CO 2 to the deep ocean along the continental shelf slope, particularly around the Antarctic bottom water (AABW) formation areas where much of the global bottom water is formed. However, the contribution of the formation of AABW to sequestering anthropogenic carbon ( C ant ) and its consequences remain unclear. Here, we show prominent transport of C ant (25.0 ± 4.7 Tg C yr −1 ) into the deep ocean (>2,000 m) in four AABW formation regions around Antarctica based on an integrated observational data set (1974–2018). This maintains a lower C ant in the upper waters than that of other open oceans to sustain a stronger CO 2 uptake capacity (16.9 ± 3.8 Tg C yr −1 ). Nevertheless, the accumulation of C ant can further trigger acidification of AABW at a rate of −0.0006 ± 0.0001 pH unit yr −1 . Our findings elucidate the prominent role of AABW in controlling the Southern Ocean carbon uptake and storage to mitigate climate change, whereas its side effects (e.g., acidification) could also spread to other ocean basins via the global ocean conveyor belt. Plain Language Summary The Southern Ocean is thought to uptake and store a large amount of anthropogenic CO 2 ( C ant ), but little attention has been paid to the Antarctic coastal regions in the south of 60°S, mainly due to the lack of observations. Based on an integrated data set, we discovered the deep penetration of C ant and a visible pattern of relatively high concentration of C ant along the AABW formation pathway, and the concentration of C ant along the shelf‐slope is higher than that of other marginal seas at low‐mid latitudes, implying a highly effective C ant transport in AABW formation areas. We also found strong upper‐layer CO 2 uptake and a significant acidification rate in the deep waters of the Southern Ocean due to the AABW‐driven CO 2 transport, which is 3 times faster than those in other deep oceans. It is therefore crucial to understand how the Antarctic shelf regions affect the ...