Global warming and marine carbon cycle feedbacks an future atmospheric CO2

A low-order physical-biogeochemical climate model was used to project atmos pheric carbon dioxide and global warming for scenarios developed by the Int ergovernmental Panel on Climate Change. The North Atlantic thermohaline cir culation weakens in all global warming simulations and collapses at high le vels of carbon dioxide. Projected changes in the marine carbon cycle have a modest impact on atmospheric carbon dioxide. Compared with the control, at mospheric carbon dioxide increased by 4 percent at year 2100 and 20 percent at year 2500. The reduction in ocean carbon uptake can be mainly explained by sea surface warming. The projected changes of the marine biological cyc le compensate the reduction in downward mixing of anthropogenic carbon, exc ept when the North Atlantic thermohaline circulation collapses.