Factors influencing anthropogenic carbon dioxide uptake in the North Atlantic in models of the ocean carbon cycle
- Max Planck Institute for Meteorology, Hamburg (Germany)
The uptake and storage of anthropogenic carbon in the North Atlantic is investigated using different configurations of ocean general circulation/carbon cycle models. We investigate how different representations of the ocean physics in the models, which represent the range of models currently in use, affect the evolution of CO{sub 2} uptake in the North Atlantic. The buffer effect of the ocean carbon system would be expected to reduce ocean CO{sub 2} uptake as the ocean absorbs increasing amounts of CO{sub 2}. We find that the strength of the buffer effect is very dependent on the model ocean state, as it affects both the magnitude and timing of the changes in uptake. The timescale over which uptake of CO{sub 2} in the North Atlantic drops to below preindustrial levels is particularly sensitive to the ocean state which sets the degree of buffering; it is less sensitive to the choice of atmospheric CO{sub 2} forcing scenario. Neglecting physical climate change effects, North Atlantic CO{sub 2} uptake drops below preindustrial levels between 50 and 300 years after stabilisation of atmospheric CO{sub 2} in different model configurations. Storage of anthropogenic carbon in the North Atlantic varies much less among the different model configurations, as differences in ocean transport of dissolved inorganic carbon and uptake of CO{sub 2} compensate each other. This supports the idea that measured inventories of anthropogenic carbon in the real ocean cannot be used to constrain the surface uptake. Including physical climate change effects reduces anthropogenic CO{sub 2} uptake and storage in the North Atlantic further, due to the combined effects of surface warming, increased freshwater input, and a slowdown of the meridional overturning circulation. The timescale over which North Atlantic CO{sub 2} uptake drops to below preindustrial levels is reduced by about one-third, leading to an estimate of this timescale for the real world of about 50 years after the stabilisation of atmospheric CO{sub 2}. In the climate change experiment, a shallowing of the mixed layer depths in the North Atlantic results in a significant reduction in primary production, reducing the potential role for biology in drawing down anthropogenic CO{sub 2}.
- OSTI ID:
- 21084015
- Journal Information:
- Climate Dynamics, Vol. 31, Issue 4; Other Information: doi 10.1007/s00382-008-0365-y; ISSN 0930-7575
- Country of Publication:
- United States
- Language:
- English
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