Magnitude of the CaCO3 dissolution events marking the onset of times of glaciation

The availability of CaCO3 and He-3 content results for core TT 13-72 from 4,3 km depth in the equatorial Pacific [Marcantonio et al., 1996] allows the magnitude of the excess (i,e,, over ambient) CaCO3 dissolution at the onset of marine glacial stages 10, 8, and 6 to be estimated. These three events are remarkably similar; during each ax integrated loss of about 28 g CaCO3 per cm(2) occurred. While the magnitude of this loss is consistent with that expected from the interglacial to glacial pH shifts reconstructed based on boron isotope measurements on benthic foraminifera [Sanyal et al, 1995], measurements at a number of other locations and water depths will be required before this approach can be used to evaluate the global toll of these dissolution events.