Carbonate compensation dynamics

Carbonate saturation (z sat ) and compensation (z cc ) depths change with deep‐ocean acidification and basification. We present simple, explicit, mechanistic formulas for the positions of these two critical depths. In particular z cc is expressed as a function of the mean dissolved carbonate ion concentration of the deep ocean, [CO 3 ] D , the supply of dissolvable CaCO 3 , F c , and the dissolution rate constant at the sediment‐water interface, k c , which we show to be essentially mass‐transfer controlled. Calculations reveal that z sat and z cc are today some ∼0.9 km apart and will rise and separate by as much as 1.7 km with acidification; conversely, if [CO 3 ] D increases, z sat and z cc will deepen, but their separation will asymptote to ∼0.7 km.