Distribution of carbonate ion in the deep ocean: Support for a post‐Little Ice Age change in Southern Ocean ventilation?

The distribution of CO 3 = ion concentrations in the deep sea proves difficult to reconcile with a steady state thermohaline circulation. The problem is that assuming steady state, we cannot come up with any satisfactory explanation for the 28 μ mol/kg deficiency of CO 3 = ion concentration in deep Pacific and Indian Ocean water relative to that for the source water mix. However, following Broecker et al. [1999], if we assume that during the Little Ice Age, deep water formation in the Southern Ocean was not only much stronger than now but also had lower PO 4 * and CO 3 = concentrations, then this anomaly can be explained.