As water heats, the solubility of solids (salts, sugars, etc.) goes up.
As water heats, the solubility of gases (O2, CO2, etc.) goes down.
Humanity coming from initial blissful ignorance about CO2 emissions eventually became concerned about rising atmospheric CO2.
Most emitted CO2 was actually being absorbed by oceans. This also makes the ocean acidic.
So the oceans acted like a "landfill" buffering a large amount of CO2 emissions.
Consider a duplicate earth, where Carbon is added to atmospheric O2 oxygen molecules. As long as its surface waters are not saturated with CO2, it can buffer a large fraction of the resulting CO2, with an equilibrium constant between aqueous CO2 and atmospheric CO2. At a certain point this "CO2 landfill" or rather "CO2 seafill" saturates. Assuming for simplicity a constant CO2 emission rate, thus without increasing the rate of CO2 emission, atmospheric CO2 rises at an initial rate (slower than CO2 emission rate, since a large fraction is initially absorbed by the ocean surface waters); until surface waters are (near) saturation, at which point atmospheric CO2 starts rising at a much higher rate since the surface waters no longer absorb significant amounts of CO2.
If one then desparately and miraculously succeeds in somehow halting continued excess CO2 emissions, the globe will still heat due to the added atmospheric CO2, also heating these surface waters, decreasing gaseous solubilities, resulting not just in aqueous O2 depletion but also sadly in "CO2 blowback": the large fraction of CO2 historically dissolved in the surface waters turns back into the atmosphere, even though miraculously excess antropogenic CO2 emissions were halted!
From a "carbon credits" perspective, where players are traditionally viewed as nations and corporations, surface waters rear their head and releases the historical CO2 debth.