You've to take care when reading things about the ocean and CO2 on the internet. This article for example is wrong:
takes the solubility of CO2 in water, then calculates a CO2 release. They use a solubility factor that is valid at a certain temperature and at a certain partial pressure of CO2. This is fine, if we would have an infinite atmosphere and the partial pressure of CO2 would not change because of the CO2 that was added to the atmosphere.
However, we don't have an infinite atmosphere and when CO2 is added to the atmosphere, the partical pressure of CO2 increases. This article fails to include that the solubility also depends on the partial pressure of CO2 in the atmosphere. And as a matter of fact, partial pressure has a far more powerful influence on the solubility so this is a very, very big oversight.
Because: if you increase the pressure of a gas above the ocean, then the extra gas has only 1 escape left: into the ocean, until the partial pressure in the ocean balances the pressure above it.
This article has a better plot of CO2 content of the oceans.
Especially this plot: http://earthobservatory.nasa.gov/Features/OceanCarbon/images/henrys_law_CO2_rt.gif
The plot shows the oceanic CO2 content as a function of temperature, but at different CO2 levels in the atmosphere.
If you'd assume a constant partical pressure, you would follow the curve of CO2/Temperature down, as the CO2 goes down with temperature.
But if you take into account that a release would increase the partial pressure, then you'd have to leave the original CO2/temp curve you were on, and jump to a higher curve of CO2/T that is representative of a higher pressure.
This illustrates that only taking temperature into account is misleading.
So while it may be true that huge amounts of CO2 are transferred from warm to cold ocean waters, this process occurs at a stable partial pressure because it's a matter of regional differences, it's not a global effect. This is purely temperature dependent. You cannot and should not use this as "proof" that oceans are able to significanly increase the CO2 content of the atmosphere on a global scale by temperature alone.
These articles offers an interesting mechanism for CO2 releases from the oceans:
A bottom ocean layer that's chock full of CO2 from decay of organic material (which can be considered as having a very high partial pressure equivalent), is transported towards the surface and is confronted with the very low partial pressure of the atmosphere. Naturally, significant amounts of carbon are then released.
This article gives a very nice summary of all the cycles involving CO2 and oceans: