Decadal increases of anthropogenic CO<sub>2</sub> in the subtropical South Atlantic Ocean along 30°S

Murata, Akihiko; Kumamoto, Yuichiro; Sasaki, Ken‐ichi; Watanabe, Shuichi; Fukasawa, Masao

doi:10.1029/2007jc004424

Cited by 38 publications

(65 citation statements)

References 56 publications

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“…1, we find the highest inventory rate of DIC and DIC abio of all our areas in the Atlantic (Table 1). This is in contrast to the results presented by Murata et al (2008) who found an inventory rate of only 0.43-0.49 mol m −2 yr −1 , (although for C ant ) partly using the same data as in this study (i.e. the repeats of WOCE section A10 in 1993 and 2003).…”

Section: T Tanhua and R F Keeling: Changes In Column Inventories Ocontrasting

confidence: 56%

Changes in column inventories of carbon and oxygen in the Atlantic Ocean

Tanhua

2012

Biogeosciences

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Abstract. Increasing concentrations of dissolved inorganic carbon (DIC) in the interior ocean are expected as a direct consequence of increasing concentrations of CO 2 in the atmosphere. This extra DIC is often referred to as anthropogenic carbon (C ant ), and its inventory, or increase rate, in the interior ocean has previously been estimated by a multitude of observational approaches. Each of these methods is associated with hard to test assumptions since C ant cannot be directly observed. Results from a simpler concept with fewer assumptions applied to the Atlantic Ocean are reported on here using two large data collections of carbon relevant bottle data. The change in column inventory on decadal time scales, i.e. the storage rate, of DIC, respiration compensated DIC and oxygen is calculated for the Atlantic Ocean. We report storage rates and the confidence intervals of the mean trend at the 95 % level (CI), reflecting the mean trend but not considering potential biasing effects of the spatial and temporal sampling. For the whole Atlantic Ocean the mean trends for DIC and oxygen are non-zero at the 95 % confidence level: DIC: 0.86 (CI: 0.72-1.00) and oxygen: −0.24 (CI: −0.41-(−0.07)) mol m −2 yr −1 . For oxygen, the whole Atlantic trend is dominated by the subpolar North Atlantic, whereas for other regions the O 2 trends are not significant. The storage rates are similar to changes found by other studies, although with large uncertainty. For the subpolar North Atlantic the storage rates show significant temporal and regional variation of all variables. This seems to be due to variations in the prevalence of subsurface water masses with different DIC and oxygen concentrations leading to sometimes different signs of storage rates for DIC compared to published C ant estimates. This study suggest that accurate assessment of the uptake of CO 2 by the oceans will require accounting not only for processes that influence C ant but also additional processes that modify CO 2 storage.

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Section: T Tanhua and R F Keeling: Changes In Column Inventories Ocontrasting

confidence: 56%

Changes in column inventories of carbon and oxygen in the Atlantic Ocean

Tanhua

2012

Biogeosciences

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“…The low storage is supported by databased estimates (e.g., Poisson and Chen, 1987;Gruber, 1998;Hoppema et al, 2001) that rely on factors such as the very high Revelle factor of these waters, the relatively short contact time with the surface between upwelling and subduction and decreased CO 2 uptake due to the presence of seaice. However, these findings are contradicted by the detection and accumulation of CFCs in Antarctic deep and bottom waters (e.g., Meredith et al, 2001;Orsi et al, 2002) and the C ANT accumulation detected south of Australia (McNeil et al, 2001) and in the South Atlantic Ocean (Murata et al, 2008), or using the TTD technique for the whole Southern Ocean (Waugh et al, 2006). Recent carbon-based studies also detect significant C ANT accumulation in deep and bottom waters of the Southern Ocean (Lo Monaco et al, 2005a, b;Sandrini et al, 2007).…”

Section: Introductionmentioning

confidence: 55%

Estimating the storage of anthropogenic carbon in the subtropical Indian Ocean: a comparison of five different approaches

et al. 2009

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Abstract. The subtropical Indian Ocean along 32 • S was for the first time simultaneously sampled in 2002 for inorganic carbon and transient tracers. The vertical distribution and inventory of anthropogenic carbon (C ANT ) from five different methods: four data-base methods ( C*, TrOCA, TTD and IPSL) and a simulation from the OCCAM model are compared and discussed along with the observed CFC-12 and CCl 4 distributions. In the surface layer, where carbonbased methods are uncertain, TTD and OCCAM yield the same result (7±0.2 molC m −2 ), helping to specify the surface C ANT inventory. Below the mixed-layer, the comparison suggests that C ANT penetrates deeper and more uniformly into the Antarctic Intermediate Water layer limit than estimated from the much utilized C* method. Significant CFC-12 and CCl 4 values are detected in bottom waters, associated with Antarctic Bottom Water. In this layer, except for C* and OCCAM, the other methods detect significant C ANT values. Consequently, the lowest inventory is calculated using the C* method (24±2 molC m −2 ) or OCCAM (24.4±2.8 molC m −2 ) while TrOCA, TTD, and IPSL lead to higher inventories (28.1±2.2, 28.9±2.3 and 30.8±2.5 molC m −2 respectively). Overall and despite the uncertainties each method is evaluated using its relationship with tracers and the knowledge about water masses in the subtropical Indian Ocean. Along 32 • S our best estimate for the mean C ANT specific inventory is 28±2 molC m −2 . Comparison exercises for data-based C ANT methods along with Correspondence to: M.Álvarez (marta.alvarez@uib.es) time-series or repeat sections analysis should help to identify strengths and caveats in the C ANT methods and to better constrain model simulations.

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“…The presence of the western boundary current in the South Atlantic Ocean means that the C ant signal penetrates deeper and is larger in the western half of the basin compared to the eastern half Ríos et al, 2010;Vázquez-Rodríguez et al, 2009a). Similarly, Murata et al (2008) show that the C ant signal in Subantarctic Mode Water (SAMW) can be ∼ 7 µmol kg −1 higher west of 15 • W compared to the east. Mode and intermediate water formation constitute a major pathway of C ant into the South Atlantic Ocean interior (McNeil et al, 2001;Sabine et al, 2004).…”

Section: Published By Copernicus Publications On Behalf Of the Europementioning

confidence: 88%

Rapid acidification of mode and intermediate waters in the southwestern Atlantic Ocean

et al. 2015

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Abstract.Observations along the southwestern Atlantic WOCE A17 line made during the Dutch GEOTRACES-NL programme (2010)(2011) were compared with historical data from 1994 to quantify the changes in the anthropogenic component of the total pool of dissolved inorganic carbon ( C ant ). Application of the extended multilinear regression (eMLR) method shows that the C ant from 1994 to 2011 has largely remained confined to the upper 1000 dbar. The greatest changes occur in the upper 200 dbar in the Subantarctic Zone (SAZ), where a maximum increase of 37 µmol kg −1 is found. South Atlantic Central Water (SACW) experienced the highest rate of increase in C ant , at 0.99 ± 0.14 µmol kg −1 yr −1 , resulting in a maximum rate of decrease in pH of 0.0016 yr −1 . The highest rates of acidification relative to C ant , however, were found in Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW). The low buffering capacity of SAMW and AAIW combined with their relatively high rates of C ant increase of 0.53 ± 0.11 and 0.36 ± 0.06 µmol kg −1 yr −1 , respectively, has lead to rapid acidification in the SAZ, and will continue to do so whilst simultaneously reducing the chemical buffering capacity of this significant CO 2 sink.

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

Cited by 38 publications

References 56 publications

Changes in column inventories of carbon and oxygen in the Atlantic Ocean

Changes in column inventories of carbon and oxygen in the Atlantic Ocean

Estimating the storage of anthropogenic carbon in the subtropical Indian Ocean: a comparison of five different approaches

Rapid acidification of mode and intermediate waters in the southwestern Atlantic Ocean

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

Cited by 38 publications

References 56 publications

Changes in column inventories of carbon and oxygen in the Atlantic Ocean

Changes in column inventories of carbon and oxygen in the Atlantic Ocean

Estimating the storage of anthropogenic carbon in the subtropical Indian Ocean: a comparison of five different approaches

Rapid acidification of mode and intermediate waters in the southwestern Atlantic Ocean

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Product

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