Long-term variability of the terrestrial and oceanic carbon sinks and the budgets of the carbon isotopes 13C and 14C ...

• Main Authors: Joos, Fortunat, Bruno, Michele
• Format: Text
• Language: unknown
• Published: American Geophysical Union 1998
• Subjects: 530 Physics; ice core
• Online Access: https://dx.doi.org/10.48350/158808; https://boris.unibe.ch/158808/

The long-term variability in the terrestrial and oceanic uptake of anthropogenic carbon is investigated. Ice core and direct observations of atmospheric CO2 and 13C are used for the last 200 years. An inverse method called double deconvolution is applied. It is found that the biosphere turned from a carbon source of about 0.5 Gt C yr−1 into a sink of 1 Gt C yr−1 during the first half of this century. This is in qualitative agreement with earlier reconstructions based on atmospheric CO2 data and implies a terrestrial sink to compensate land use emissions during the last five decades. Oceanic and biospheric carbon uptakes are estimated to be 0.9±1.0 and l.l±1.0 Gt C yr−1 as averaged over the 1970–1990 period. Hence ocean uptake is on the low side of current estimates, but our results may be biased as δ13C observations between 1956 and 1982 are missing. Additional uncertainties in calculated carbon sinks are due to uncertainties in model parameters and in fossil emission estimates. Prior to 1950, uncertainties ...