Anthropogenic CO(2) in the Southern Ocean: Distribution and inventory at the Indian-Atlantic boundary (World Ocean Circulation Experiment line I6)

• Published in: Journal of Geophysical Research
• Main Authors: Lo Monaco, C, Metzl, N, Poisson, A, Brunet, C, Schauer, B
• Format: Article in Journal/Newspaper
• Language: English
• Published: Amer Geophysical Union 2005
• Subjects: anthropogenic CO2; Southern Ocean; WOCE; Antarctic; Indian; Prydz Bay; Weddell; Weddell Sea; Antarc*; Antarctica; North Atlantic
• Online Access: https://archimer.ifremer.fr/doc/00233/34409/32823.pdf; https://doi.org/10.1029/2004JC002643; https://archimer.ifremer.fr/doc/00233/34409/

The Southern Ocean, where various water masses are formed ( mode, intermediate, deep, and bottom waters), has a high potential to absorb anthropogenic CO(2) ( C ant). However, most data-based and model estimates indicate low C(ant) inventories south of 50 degrees S. In order to investigate this paradox, the distribution of C(ant) is estimated between South Africa and Antarctica ( World Ocean Circulation Experiment ( WOCE) line I6) based on a back-calculation technique previously used in the North Atlantic ( Kortzinger et al., 1998) and adapted here for application in the Southern Ocean. At midlatitudes (30 degrees-50 degrees S), formation and spreading of mode and intermediate waters results in a deep penetration of C(ant) ( down to 2000 m). South of 50 degrees S, significant concentrations of C ant were estimated in Circumpolar Deep Water (> 10 mu mol/ kg) and Antarctic Bottom Water ( AABW) ( 20-25 mu mol/ kg). Higher concentrations are detected along the continental slope in AABW presumably formed in Prydz Bay compared to AABW of Weddell Sea origin. The distribution of C(ant) obtained north of 50 degrees S compares well with previous databased and model estimates, but large disagreements are found in the south. However, although transient tracers are not used in the back-calculation technique employed here, the distribution of C(ant) is remarkably well correlated with CFCs. We reevaluated the column inventories of C ant for the Southern Ocean and found higher values at high latitudes ( 70-90 mol/m(2)) compared to the subtropical/subantarctic region (40-80 mol/m(2)). These results support the idea that deep and bottom water formation in the Southern Ocean is a key process in the natural sequestration of anthropogenic CO2.