Sanders, R., Morris, P. J. , Stinchcombe, M. C. , Charalampopoulou, A., Lucas M., Thomalla S.J.
Abstract

The oceanic biological carbon pump (BCP), a large (10 GT C yr−1) component of the global carbon cycle, is dominated by the sinking (export) of particulate organic carbon (POC) from surface waters. In the deep ocean, strong correlations between downward fluxes of biominerals and POC (the so-called ‘ballast effect’) suggest a potential causal relationship, the nature of which remains uncertain. We show that similar correlations occur in the upper ocean with high rates of export only occurring when biominerals are also exported. Exported particles are generally biomineral rich relative to the upper ocean standing stock, due either to: (1) exported material being formed from the aggregation of a biomineral rich subset of upper ocean particles; or (2) the unfractionated aggregation of the upper ocean particulate pool with respiration then selectively removing POC relative to biominerals until particles are dense enough to sink.

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Figure 4 caption: POC (a) calcite, (b) opal ratios in exported and upper ocean particulate pools at 18 sites in the subpolar, subtropical and tropical Atlantic Ocean. Full symbols are from the AMT study [Thomalla et al., 2008]. Empty symbols are new observations reported here from the Iceland Basin in 2007 (auxiliary material). Note the broken axis required to include all data points.

Figure 4 caption: POC (a) calcite, (b) opal ratios in exported and upper ocean particulate pools at 18 sites in the subpolar, subtropical and tropical Atlantic Ocean. Full symbols are from the AMT study [Thomalla
et al., 2008]. Empty symbols are new observations reported here from the Iceland Basin in 2007 (auxiliary
material). Note the broken axis required to include all data points.

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