Deglacial CO 2 buildup: Constraints on the coral-reef model

Abstract

The coral-reef hypothesis of degalcial CO 2 buildup in the atmosphere can account for about one-half of the signal seen in ice cores, assuming additional coral-reef growth releases 2 atmospheric carbon masses (ACM). The carbonate dissolution signal on the deep sea floor suggest titration of only 1 ACM. At least 4 ACM of CO 2 must be made available to satisfy the requirements of pCO 2-increases, growth of biosphere and of sedimentary carbon pool, carbonate dissolution on the sea floor, and saturation of newly introduced meltwater. A drop in ocean fertility is called for to provide the missing CO 2. Such a drop is evident in deep-sea cores from the western equatorial Pacific. CO 2 buildup appears to occur as a step, near 13,500 years B.P. Dissolution on the deep sea floor begins near 11,000 years B.P. The difference of 2500 years may describe a mixing lag due to meltwater input (the “Worthington Effect”).