Warmer water holds less dissolved gases of all kinds, including CO2. You can see this yourself by heating water in your kitchen. Well below the boiling point, you can observe tiny bubbles, which are composed of nitrogen and oxygen dissolved in the water coming out of solution. The oceans will eventually become carbon sources, not carbon sinks, if they warm enough, but that's not projected to happen this century.
However, there are regions of the oceans which currently absorb lots of CO2 which will absorb much less as time goes on. One important example is the AMOC, which, by turning over lots of water, helps sink surface dissolved CO2 into the deeper ocean. In recent years, oceanographers have observed a weakening of the AMOC, which was predicted but is happening much earlier than expected. This is one of the important planetary tipping points, which could cause a dramatic shift in the planet's climate.
But don't worry -- the Trump administration is defunding programs like the Office of Oceanic and Atmospheric Research, decommissioning the Ocean Observatories Initiative, and is planning to shutter NOAA's research arm altogether -- thus solving the problem once and for all.