This is shown as a diagram, with the historic average taken out because it is known.
You can see the computer model heads to equilibrium at 40%, sharing the C14 in proportion between the 3 sinks and ignoring the deep ocean. It even drops faster at the start, showing how wrong the shape is. As elsewhere, the real curve is a perfect straight line on log paper. This means a perfect e-kt curve and one big sink which takes the lot.
No, what is needed to explain the graph is a huge reservoir which can absorb every last bit of CO2 and its tiny C14 tracer without blinking, a reservoir incredibly bigger than the air and the land and even the ocean surface. Only the deep ocean qualifies. Conventional wisdom is that it would take a thousand years for the deep sea to absorb anything, simply because we know the layers of water do not mix. Clearly this does not apply to the gas CO2. CO2 is dramatically more soluble at high pressure and low temperature, as in the deep oceans. Remember 10 metres = 1 atmosphere, so even 100metres down is 10 atmospheres. Plenty to compress CO2. Unless someone can explain where all the CO2 goes, the obvious explanation is simple enough. It disappears into the biggest hole there is.