That "just enough" is probably half of what is presently in the atmosphere. The oceans have absorbed huge amounts of what we've emitted, and would disgorge it accordingly. The CO2 level in 1900 was about 300 ppm; now its 400. To make a substantial reversal in climate change by only removing CO2 from the atmosphere, we'd have to make a massive stride by 2050.
The oceans may also end up being a higher priority at least at first because there is already evidence that acidification caused by absorption of excess atmospheric carbon us causing ocean ecosystems to break down while disruption on land is still relatively minor.
I'm not sure you can target oceanic CO2 over CO2 in the atmosphere. Ocean acidification is an equilibrium process driven by the partial pressure of CO2 in the atmosphere increasing.
If you start reversing acidification, the ocean is just going to start pulling in more CO2 from the atmosphere.
