Carbonate compensation dynamics

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Abstract

[1] Carbonate saturation (zsat) and compensation (zcc) depths change with deep-ocean acidification and basification. We present simple, explicit, mechanistic formulas for the positions of these two critical depths. In particular zcc is expressed as a function of the mean dissolved carbonate ion concentration of the deep ocean, [CO3]D, the supply of dissolvable CaCO3, Fc, and the dissolution rate constant at the sediment-water interface, kc, which we show to be essentially mass-transfer controlled. Calculations reveal that zsat and zcc are today some ∼0.9 km apart and will rise and separate by as much as 1.7 km with acidification; conversely, if [CO3]D increases, zsat and zcc will deepen, but their separation will asymptote to ∼0.7 km.

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