Anthropogenic Carbon Dioxide (CO2) Amounts and Fluxes between the Atmosphere, the Ocean, and the Biosphere

Abstract

The author has developed one dimensional semi-empirical atmosphere-ocean-biosphere model (1DAOBM) based on the four-box presentation. Firstly, the author has analysed that the model development can be based on the two elements: 1) the four box-model containing two ideal mixing components (the atmosphere and the ocean), one plug flow component with four different residence times (the biosphere), and the outlet (the intermediate & deep ocean), 2) the ocean’s capacity to dissolve anthropogenic CO2 emissions of the present century. The surface ocean part is based on the known dissolution chemical equations. The net flux rate from the surface ocean into the deep ocean is based on the empirical data. The removal of the anthropogenic CO2 from the atmosphere is based on the huge carbon cycle flux rates of the dissolution pump and the biosphere carbon cycle, which remove yearly about 26% of CO2 from the atmosphere to other reservoirs and, at the same time, recycle back natural and anthropogenic carbon. The simulations of the atmospheric net CO2 rate by 1DAOBM from 1960 to 2013 show fairly good similarity to the measured values: r2 = 0.75 and the standard error of estimate 0.68 GtC/y, which means the standard error of 12% at the present emission rate of about 10 GtC/y. The simulations show that the present anthropogenic CO2 fraction in the atmosphere is 7.7%, and it explains the observed δ13C value of -8.4‰ extremely well. Also, the reduction of δ13C in the ocean from 1900 to 2013, simulated to be -0.6‰, is close to the observed values. The 1DAOBM has been used also to simulate the fluxes and CO2 concentration trends corresponding to the projection RCP4.5 of IPCC. These results deviate from the IPCC’s results in the descending phase of the CO2 emissions. The mean residence time of the total atmospheric CO2 concentration change is 32 years and that of the anthropogenic CO2 change is 15 years, according to 1DAOBM simulations.