Buffered versus non-buffered ocean carbon reservoir variations: Application to the sensitivity of atmospheric pCO2 to ocean circulation changes

• Published in: Geophysical Research Letters
• Main Authors: d'Orgeville, M, England, MH, Sijp, WP, Dorgeville, Marc
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Geophysical Union 2011
• Subjects: 14 Life Below Water; North Atlantic
• Online Access: http://hdl.handle.net/1959.4/unsworks_41965; https://doi.org/10.1029/2011GL049823

Changes in the ocean circulation on millenial timescales can impact the atmospheric CO2 concentration by two distinct mechanisms: either by modifying the non-buffered ocean carbon storage (through changes in the physical and biological oceanic pumps) or by directly varying the surface mean oceanic partial pressure of pCO2 (through changes in mean surface alkalinity, temperature or salinity). The equal importance of the two mechanisms is illustrated here by introducing a diagnostic buffered carbon budget on the results of simulations performed with an Earth System Climate Model. For all the circulation changes considered in this study (due to a freshening of the North Atlantic, or a change in the Southern Hemisphere Westerly winds), the sign of the atmospheric CO2 response is opposite to the sign of the non-buffered ocean carbon storage change, indicating a transfer of carbon between ocean and atmosphere reservoirs. However the concomitant changes in the buffered ocean carbon reservoir can either greatly enhance or almost inhibit the atmospheric response depending on its sign. This study also demonstrates the utility of the buffered carbon budget approach in diagnosing the transient response of the global carbon cycle to climatic variations.