Based on the simulations using the University of Victoria Earth System Climate Model under the scenarioof RCP8.5, the responses of ocean carbon cycle to increasing atmospheric CO_2 and climate change from year 1800to 2500 were analyzed. Relative to the simulation case with no climate change, the simulation with climate sensitivity 3.0 K shows that in 2100,due to the increase of atmospheric CO_2 concentrations simulated sea surface temperatureincreases by 2.7 K, the intensity of the North Atlantic deep water formation reduces by 4.5 Sv, and oceanic uptake of anthropogenic CO_2 decreases by 0.8 Pg C. As for ocean column inventory of anthropogenic CO_2,climate change isfound to have a large effect in the North Atlantic. During 18002500, compared to the simulation with no climatechange, climate change causes a reduction of total anthropogenic CO_2 column inventory in the entire ocean andNorth Atlantic by 23.1% and 32.0%, respectively. A set of simulations with climate sensitivity varying from 0.5 K to4.5 K show that with a greater climate sensitivity climate change would have a larger effect in reducing the ocean'sability to absorb CO_2 from the atmosphere.