The Mid-Brunhes dissolution interval (MBDI) represents a period of global carbonate dissolution, lasting several hundred thousand years, centred around Marine Isotope Stage (MIS) 11. Here we report the effects of dissolution in ODP core 982, taken from 1134m in the North Atlantic. Paradoxically, records of atmospheric CO2 from Antarctic ice-cores reveal no long term trend over the last 400 kyr and suggest that CO2 during MIS I I was no higher than during the present interglacial. We suggest that a global increase in pelagic carbonate production during this period, possibly related to the proliferation of the Gephyrocapsa coccolithophore, could have altered marine carbonate chemistry in such a way as to drive increased dissolution under the constraints of steady state. An increase in the production of carbonate in surface waters would cause a drawdown of global carbonate saturation and increase dissolution at the seafloor. In order to reconcile the record of atmospheric CO2 variability we suggest that an increase in the flux of organic matter from the surface to deep ocean, associated with either a net increase in primary production or the enhanced ballasting effect provided by an increased flux of CaCO3, could have countered the effect of increased calcification on CO2. (c) 2006 Elsevier Ltd. All rights reserved.
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