The ocean in general is by far the largest carbon (and heat) sink. Some of that is from photosynthesis--about 70% of all the photosynthesis on the planet happens in the ocean --and some of it is just brute absorption of CO2. That system is showing signs of flagging also, as increased temperatures reduce water's ability to hold CO2 and disruptions to thermohaline circulation hamper oceanic photosynthesis, but it was really land-based sinks that dramatically failed this year (partially because of all the wildfires).
The ocean in general is by far the largest carbon (and heat) sink. Some of that is from photosynthesis--about 70% of all the photosynthesis on the planet happens in the ocean --and some of it is just brute absorption of CO2. That system is showing signs of flagging also, as increased temperatures reduce water's ability to hold CO2 and disruptions to thermohaline circulation hamper oceanic photosynthesis, but it was really land-based sinks that dramatically failed this year (partially because of all the wildfires).