Decadal increases of anthropogenic CO2 in the subtropical South Atlantic Ocean along 30°S

• Published in: Journal of Geophysical Research: Oceans 2008-06, Vol.113 (C6), p.n/a
• Main Authors: Murata, Akihiko, Kumamoto, Yuichiro, Sasaki, Ken'ichi, Watanabe, Shuichi, Fukasawa, Masao
• Format: Article
• Language: English
• Subjects: Anthropogenic CO2; CLIVAR/CO2; dissolved inorganic carbon; Earth sciences; Earth, ocean, space; Exact sciences and technology
• ISSN: 0148-0227; 2156-2202
• DOI: 10.1029/2007JC004424

Using high‐quality data for dissolved inorganic carbon and related properties obtained about 10 years apart (1992/1993–2003), we examined decadal increases of anthropogenic CO2 (ΔnCTCAL) along 30°S (WHP A10 section) in the subtropical South Atlantic. Significant ΔnCTCAL was detectable down to an isopycnal surface of σθ = 27.3 (∼1000 m water depth). Averaged ΔnCTCAL in Sub‐Antarctic Mode Water (SAMW; 26.6–27.0 σθ, 350–700 m) was 6.8 ± 1.6 μmol kg−1 and that in Antarctic Intermediate Water (AAIW; 27.1–27.4 σθ, 700–1200 m) was 3.6 ± 1.4 μmol kg−1. In SAMW, ΔnCTCAL was higher by ∼7 μmol kg−1 west of 15°W than east of it, while ΔnCTCAL in AAIW did not show such a distinct east‐west difference. For deep waters, significant ΔnCTCAL was detected in Antarctic Bottom Water at depths greater than 4500 m in the Cape Basin (longitude 2°E–10°E). No significant ΔnCTCAL could be detected for North Atlantic Deep Water (NADW). We attributed ΔnCTCAL being higher west of 15°W in SAMW to differences of water mass distributions and flows. From a water column inventory, we estimated the uptake rate of anthropogenic CO2 over the decade from 1992/1993 to 2003 to be 0.6 ± 0.1 mol m−2 a−1, which is half the rate in the South Pacific (1.0 ± 0.4 mol m−2 a−1).