The amount of carbon stored in continental reservoirs such as soils, sediments and the biosphere greatly exceeds the amount of carbon in the atmosphere1. As such, small variations in the residence time of organic carbon in these reservoirs can produce large variations in the atmospheric inventory of carbon dioxide. One such reservoir is the Ganges–Brahmaputra system draining the Himalayas, which represents one of the largest sources of terrestrial biospheric carbon to the ocean2. Here, we examine the radiocarbon content of river sediments collected from the Ganges–Brahmaputra drainage basin to determine the residence time of organic carbon in this reservoir. We show that the average age of biospheric organic carbon in the drainage basin ranges from 0.5 to 17 thousand years. The radiocarbon age of plant-derived fatty acids—a proxy for labile terrestrial vegetation—ranges from just 0.05 to 1.3 thousand years. We propose that the bulk ages can be explained by the existence of a refractory, slowly cycling component of the organic carbon pool that is mixed with a younger labile pool. We estimate that this refractory component has an average age of over 15,000 years, and represents up to 20% of total biospheric carbon exported by the Ganges–Brahmaputra system. We suggest that global warming might destabilize this ancient pool of carbon, if warming stimulates microbial decomposition of organic carbon reserves.
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Sabine, C. L. et al. The oceanic sink for anthropogenic CO2 . Science 305, 367–371 (2004).
Galy, V. et al. Efficient organic carbon burial in the Bengal fan sustained by the Himalayan erosional system. Nature 450, 407–410 (2007).
Berner, R. A. The long-term carbon cycle, fossil fuels and atmospheric composition. Nature 426, 323–326 (2003).
Hayes, J. M. & Waldbauer, J. R. The carbon cycle and associated redox processes through time. Phil. Trans. R. Soc. B 361, 931–950 (2006).
Galy, V., Beyssac, O., France-Lanord, C. & Eglinton, T. I. Recycling of graphite during Himalayan erosion: A geological stabilization of carbon in the crust. Science 322, 943–945 (2008).
Garrels, R. M., Lerman, A. & Mackenzie, F. T. Controls of atmospheric O2 and CO2: Past, present and future. Am. Sci. 64, 306–315 (1976).
Sarmiento, J. & Gruber, N. in Ocean Biogeochemical Dynamics (eds Sarmiento, J. & Gruber, N.) Ch. 10, 392–453 (Princeton Univ. Press, 2006).
Trumbore, S. Comparison of carbon dynamics in tropical and temperate soils using radiocarbon measurements. Glob. Biogeochem. Cycles 7, 275–290 (1993).
Blair, N. E., Leithold, E. L. & Aller, R. C. From bedrock to burial: The evolution of particulate organic carbon across coupled watershed-continental margin systems. Mar. Chem. 92, 141–156 (2004).
Aufdenkampe, A. K. et al. Organic matter in the Peruvian headwaters of the Amazon: Compositional evolution from the Andes to the lowland Amazon mainstem. Org. Geochem. 38, 337–364 (2007).
Galy, V., France-Lanord, C. & Lartiges, B. Loading and fate of particulate organic carbon from the Himalaya to the Ganga–Brahmaputra delta. Geochim. Cosmochim. Acta 72, 1767–1787 (2008).
Hedges, J. I. et al. Compositions and fluxes of particulate organic material in the Amazon River. Limnol. Oceanogr. 31, 717–738 (1986).
Bouchez, J. et al. Oxidation of petrogenic organic carbon in the Amazon floodplain as a source of atmospheric CO2 . Geology 38, 255–258 (2010).
Drenzek, N. et al. A new look at old carbon in active margin sediments. Geology 37, 239–242 (2009).
Drenzek, N. J., Montluçon, D. B., Yunker, M. B., Macdonald, R. W. & Eglinton, T. I. Constraints on the origin of sedimentary organic carbon in the Beaufort Sea from coupled molecular 13C and 14C measurements. Mar. Chem. 103, 146–162 (2007).
Hilton, R. G., Galy, A., Hovius, N. & Horng, M. J. Efficient transport of fossil organic carbon to the ocean by steep mountain rivers: An orogenic carbon sequestration mechanism. Geology 39, 71–74 (2011).
Mayorga, E. et al. Young organic matter as a source of carbon dioxide outgassing from Amazonian rivers. Nature 436, 538–541 (2005).
Raymond, P. A. et al. Controls on the variability of organic matter and dissolved inorganic carbon ages in northeast US rivers. Mar. Chem. 92, 353–366 (2004).
Galy, V., Eglinton, T., France-Lanord, C. & Sylva, S. The provenance of vegetation and environmental signatures encoded in vascular plant biomarkers carried by the Ganges–Brahmaputra rivers. Earth Planet. Sci. 304, 1–12 (2011).
Burbank, D. et al. Decoupling of erosion and precipitation in the Himalayas. Nature 426, 652–655 (2003).
Trumbore, S. Radiocarbon and soil carbon dynamics. Annu. Rev. Earth Planet. Sci. 37, 47–66 (2009).
Eglinton, T. I. et al. Variability in radiocarbon ages of individual organic compounds from marine sediments. Science 277, 796–799 (1997).
Galy, A. & France-Lanord, C. Weathering processes in the Ganges–Brahmaputra basin and the riverine alkalinity budget. Chem. Geol. 159, 31–60 (1999).
IPCC, in Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (eds Solomon, S. et al.) (Cambridge Univ. Press, 2007).
Kirschbaum, M. The temperature dependence of soil organic matter decomposition, and the effect of global warming on soil organic C storage. Soil Biol. Biochem. 27, 753–760 (1995).
Zimov, S. A., Schuur, E. A. G. & Chapin, F. S. Permafrost and the global carbon budget. Science 312, 1612–1613 (2006).
RSP. Spatial representation and analysis of hydraulic and morphological data. Report No. FAP 24, (Water Resources Planning Organization (WARPO), 1996).
Galy, V., Bouchez, J. & France-Lanord, C. Determination of total organic carbon content and δ13C in carbonate rich detrital sediments. Geostandards Geoanalytical Res. 31, 199–207 (2007).
Eglinton, T. I., Aluwihare, L. I., Bauer, J. E., Druffel, E. R. M. & McNichol, A. P. Gas chromatographic isolation of individual compounds from complex matrices for radiocarbon dating. Anal. Chem. 68, 904–912 (1996).
Santos, G. M., Southon, J. R., Drenzek, N. J. & Ziolkowski, L. A. Blank assessment for ultra-small radiocarbon samples: Chemical extraction and separation versus AMS. Radiocarbon 52, 1322–1335 (2010).
We thank M. Rahman (Dhaka University) and A. Gajurel (Tribhuvan University) for their assistance during fieldwork in Bangladesh and Nepal. We thank D. Montluçon for technical support. We thank S. Jenouvrier for assistance with statistical analysis of the data. We thank C. France-Lanord for his support and insightful comments. This study was supported by the US National Science Foundation (Grants OCE-0851015 and OCE-0928582).
The authors declare no competing financial interests.
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Galy, V., Eglinton, T. Protracted storage of biospheric carbon in the Ganges–Brahmaputra basin. Nature Geosci 4, 843–847 (2011). https://doi.org/10.1038/ngeo1293
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