Saturated Oceans

The oceans are losing their ability to absorb CO₂ as they continue to warm

And we can see this variability clearly during different climate cycles marked by changes in average sea surface temperature.

Research strongly indicates that the Southern Pacific Ocean is at its CO₂ saturation level .

Bottom red line is the measured decrease in ocean uptake rate

And its the SPO that matters the most:

And this just got published Bottom line - Ocean uptake in North Atlantic is down by about 60% of the long term average!

The Chemisty of how CO₂ is actually absorbed by the Oceans:

So CO₂ combines with water to produce carbonic acid which releases Hydrogen ions (H⁺) into the water which makes it more acidic. Hydrogen ions in ocean surface waters are now 25 percent higher than in the pre-industrial era, with an additional 75-percent increase projected by 2100.

In turn this build up of H⁺ leds to a dissolution of carbonate (CO₃^-2) back to Bicarbonate and the subsequent loss of raw materials for sheels, reefs, etc (i.e. reduction in Calcium Carbonate part of the cycle).

And its these cycles that get saturated

Basically this graphic is simply showing that the ocean chemistry is going to change, perhaps significantly, as increasing atmospheric CO₂ ultimately means increase transformation to more Dissolved Inorganic Carbon in the ocean in addition to Ocean Acidification increases.