Estimating the storage of anthropogenic carbon in the subtropical Indian Ocean: a comparison of five different approaches
Type | Article | ||||||||||||
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Date | 2009-04-27 | ||||||||||||
Language | English | ||||||||||||
Author(s) | Alvarez M.1, Lo Monaco C.2, Tanhua T.3, Yool A.4, Oschlies A.3, Bullister J. L.5, Goyet C.6, Metzl N.2, Touratier F.6, McDonagh E.4, Bryden H. L.4 | ||||||||||||
Affiliation(s) | 1 : CSIC UIB, IMEDEA, Esporles 07190, Spain. 2 : Univ Paris 06, LOCEA IPSL, F-75252 Paris, France. 3 : IFM GEOMAR, D-24105 Kiel, Germany. 4 : NOCS, Southampton SO14 3ZH, Hants, England. 5 : NOAA, Pacific Marine Environm Lab, Seattle, WA 98115 USA. 6 : Univ Perpignan, IMAGES, F-66860 Perpignan, France. |
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Source | Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2009-04-27 , Vol. 6 , N. 4 , P. 681-703 | ||||||||||||
DOI | 10.5194/bg-6-681-2009 | ||||||||||||
WOS© Times Cited | 34 | ||||||||||||
Abstract | The subtropical Indian Ocean along 32 degrees S was for the first time simultaneously sampled in 2002 for inorganic carbon and transient tracers. The vertical distribution and inventory of anthropogenic carbon (CANT) from five different methods: four data-base methods (Delta C*, TrOCA, TTD and IPSL) and a simulation from the OCCAM model are compared and discussed along with the observed CFC-12 and CCl4 distributions. In the surface layer, where carbon-based methods are uncertain, TTD and OCCAM yield the same result (7 +/- 0.2 molC m(-2)), helping to specify the surface CANT inventory. Below the mixed-layer, the comparison suggests that CANT penetrates deeper and more uniformly into the Antarctic Intermediate Water layer limit than estimated from the much utilized Delta C* method. Significant CFC-12 and CCl4 values are detected in bottom waters, associated with Antarctic Bottom Water. In this layer, except for Delta C* and OCCAM, the other methods detect significant CANT values. Consequently, the lowest inventory is calculated using the Delta 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 degrees S our best estimate for the mean CANT specific inventory is 28 +/- 2 molC m(-2). Comparison exercises for data-based CANT methods along with time-series or repeat sections analysis should help to identify strengths and caveats in the CANT methods and to better constrain model simulations. | ||||||||||||
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