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www.biogeosciences-discuss.net/6/729/2009/
doi:10.5194/bgd-6-729-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
Estimating the storage of anthropogenic carbon in the subtropical Indian Ocean: a comparison of five different approaches
1IMEDEA (CSIC-UIB), Miquel Marqués 21, 07190 Esporles, Spain
2LOCEAN/IPSL, Université Paris 6 – place Jussieu 4, 75252 Paris, France
3IFM-GEOMAR, Düsternbrooker Weg 20, 24105 Kiel, Germany
4NOCS, Waterfront Campus European Way, Southampton, SO14 3ZH, UK
5NOAA/Pacific Marine Environmental Laboratory, Seattle, Washington, USA
6IMAGES, Université de Perpignan, 52 avenue Paul Alduy, 66860 Perpignan, France
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 (CANT) from five different methods: four data-base methods (ΔC*, TrOCA, TTD and C0IPSL 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 mol C 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 ΔC* method. Additionally, significant CFC-12 and CCl4 values are detected in bottom waters, associated with Antarctic Bottom Water. In this layer, except for ΔC* and OCCAM, the other methods detect significant CANT values. Consequently, the lowest inventory is calculated using the ΔC* method (24±2 mol C m−2) or OCCAM (24.4±2.8 mol C m−2) while TrOCA, TTD, and C0IPSL lead to higher inventories (28.1±2.2, 28.9±2.3 and 30.8±2.5 mol C 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 CANT specific inventory is 28±2 mol C 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.
Discussion Paper (PDF, 3236 KB) Interactive Discussion (Closed, 5 Comments) Final Revised Paper (BG)
Notice on Discussion StatusCitation: Álvarez, M., Lo Monaco, C., Tanhua, T., Yool, A., Oschlies, A., Bullister, J. L., Goyet, C., Metzl, N., Touratier, F., McDonagh, E., and Bryden, H. L.: Estimating the storage of anthropogenic carbon in the subtropical Indian Ocean: a comparison of five different approaches, Biogeosciences Discuss., 6, 729-796, doi:10.5194/bgd-6-729-2009, 2009. Bibtex EndNote Reference Manager XML
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