[capt. norm]

I always assumed it was because warmer seas can't hold as much dissolved CO2.

Totally valid point, that walked right past me tonight.

With the Pacific waters dropping in temperature, and right now it's in the deeper waters, the ability of the ocean waters to absorb CO₂ increase substantially.

[PSYCHO-FREEP]

Don't forget about the recent sub sea volcanic activity which is literally 1,000 times greater over the last 10 year period compared to the last 100 years. This phenomena has raised Ocean temperatures substantially, added co2 to the water and also can account for the reason there is a sudden spike in atmospheric co2 because the Oceans are already saturated.