Actually, the rate of absorption of CO2 by the oceans is tapering off. THE foremost lab that studies this is here in San Deigo, and they occasionally put up some nice blog posts (in addition to excellent pier-reviewed scientific papers). These are the guys that provide the standards for the rest of the world to measure CO2 levels in the ocean.
This one from 2013 is of particular interest:
How Much CO2 Can The Oceans Take Up?
"...starting with the simple one that as one dissolves CO2 into a given volume of seawater, there is a growing resistance to adding still more CO2."
"Human fossil fuel use is also behind a general warming trend in the oceans observed over the past 50 years that increases the resistance to CO2 uptake."
"Furthermore, in the absence of such warming, ocean mixing would normally be expected to be constantly refreshing the water at the ocean’s surface, the place where it meets with air and dissolves CO2. Instead global warming leaves surface water in place to an increasing degree thus slowing down the transfer of CO2 from the ocean surface deeper into the ocean."
The really scary thing is that long after we curb our CO2 emissions back to say even 1980 levels, the Ocean and land masses will keep releasing what they have stored up from the beginning of the industrial revolution to keep levels high.
They cover this phenomenon in this shorter blog post:
Why Has a Drop in Global CO2 Emissions Not Caused CO2 Levels in the Atmosphere to Stabilize?
"Eventually, additional emissions cuts would be required because the sinks will slowly lose their efficiency as the land and ocean start to saturate. A permanent stabilization at current levels therefore requires both an immediate 50-percent cut as well as a slow tapering thereafter, eventually approaching zero emissions. The recent stabilization in emissions might be viewed as a very small first step toward the required cuts."