An upgraded carbon-based method to estimate the anthropogenic fraction of dissolved CO2 in the Atlantic Ocean
An upgrade of classical methods to calculate the anthropogenic carbon (C ant ) signal based on estimates of the preformed dissolved inorganic carbon (C T ) is proposed and applied to modern Atlantic sections. The main progress has been the use of subsurface layer data (100–200 m) to reconstruct wate...
| Main Authors: | , , , , |
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| Format: | Text |
| Language: | English |
| Published: |
2018
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| Subjects: | |
| Online Access: | https://doi.org/10.5194/bgd-6-4527-2009 https://www.biogeosciences-discuss.net/bg-2009-56/ |
| Summary: | An upgrade of classical methods to calculate the anthropogenic carbon (C ant ) signal based on estimates of the preformed dissolved inorganic carbon (C T ) is proposed and applied to modern Atlantic sections. The main progress has been the use of subsurface layer data (100–200 m) to reconstruct water mass formation conditions and obtain better estimates of preformed properties. This practice also eliminates the need for arbitrary zero-C ant references that are usually based on properties independent of the carbon system, like the CFC content. The long-term variability of preformed total alkalinity (A T ) has been considered and the temporal variability of the air-sea CO 2 disequilibrium (ΔC dis ) included in the formulation. The change of ΔC dis with time has shown to have non-negligible biases on C ant estimates, producing a 4 μmol kg average decrease. The proposed ϕC T method produces substantial differences in the C ant inventories of the Southern Ocean and Nordic Seas (~18% of the total inventory for the Atlantic) compared with recent C ant inventories. The overall calculated Atlantic C ant inventory referenced to 1994 is 55±13 Pg C, which reconciles the estimates obtained from classical C T -based C ant calculation methods, like the ΔC*, and newly introduced approaches like the TrOCA or the TTD methods. |
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