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Title: Ocean ventilation controls the contrasting anthropogenic CO2 uptake rates between the western and eastern South Atlantic Ocean basins
The South Atlantic Ocean is an important region for anthropogenic CO2 (Canth) uptake and storage in the world ocean, yet is less studied. Here, after an extensive sensitivity test and method comparison, we applied an extended multiple linear regression (eMLR) method with six characteristic water masses to estimate Canth change or increase (ΔCanth) between 1980s and 2010s in the South Atlantic Ocean using two meridional transects (A16S and A13.5) and one zonal transect (A10). Over a period of about 25 years, the basin-wide ΔCanth was 3.86±0.14 Pg C decade-1. The two basins flanking the Mid-Atlantic Ridge had different meridional patterns of ΔCanth, yielding an average depth‐integrated ΔCanth in the top 2000 m of 0.91±0.25 mol m-2 yr-1 along A16S on the west and 0.57±0.22 mol m-2 yr-1 along A13.5 on the east. The west-east basin ΔCanth contrasts were most prominent in the tropical region (0-20°S) in the Surface Water (SW), approximately from equator to 35°S in the Subantarctic Mode Water (SAMW), and all latitudes in the Antarctic Intermediate Water (AAIW). Less Canth in the eastern basin than the western basin was caused by weaker ventilation driven by SAMW and AAIW formation and subduction and stronger Antarctic Bottom Water (AABW) formation in the former than the latter. In addition to the spatial heterogeneity, Canth increase rates accelerated from the 1990s to the 2000s, consistent with the overall increase in air-sea CO2 exchange in the South Atlantic Ocean.  more » « less
Award ID(s):
2123768
NSF-PAR ID:
10354075
Author(s) / Creator(s):
; ; ; ;
Date Published:
Journal Name:
Global biogeochemical cycles
Volume:
36
ISSN:
0886-6236
Page Range / eLocation ID:
e2021GB007265
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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    The South Atlantic Ocean is an important region for anthropogenic CO2(Canth) uptake and storage in the world ocean, yet is less studied. Here, after an extensive sensitivity test and method comparison, we applied an extended multiple linear regression method with six characteristic water masses to estimate Canthchange or increase (ΔCanth) between 1980s and 2010s in the South Atlantic Ocean using two meridional transects (A16S and A13.5) and one zonal transect (A10). Over a period of about 25 years, the basin‐wide ΔCanthwas 3.86 ± 0.14 Pg C decade−1. The two basins flanking the Mid‐Atlantic Ridge had different meridional patterns of ΔCanth, yielding an average depth‐integrated ΔCanthin the top 2000 m of 0.91 ± 0.25 mol m−2 yr−1along A16S on the west and 0.57 ± 0.22 mol m−2 yr−1along A13.5 on the east. The west‐east basin ΔCanthcontrasts were most prominent in the tropical region (0–20°S) in the Surface Water (SW), approximately from equator to 35°S in the Subantarctic Mode Water (Subantarctic Mode Water (SAMW)), and all latitudes in the Antarctic Intermediate Water (AAIW). Less ΔCanthin the eastern basin than the western basin was caused by weaker ventilation driven by SAMW and AAIW formation and subduction and stronger Antarctic Bottom Water (AABW) formation in the former than the latter. In addition to the spatial heterogeneity, Canthincrease rates accelerated from the 1990s to the 2000s, consistent with the overall increase in air‐sea CO2exchange in the South Atlantic Ocean.

     
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