A key constraint in attempts to reconstruct the patterns and rates of the ocean's thermohaline circulation during the last glacial period is the difference between the C-14 to C ratio in surface and deep water. While imperfect, it is our best index of past deep-sea ventilation rates. In this paper we review published ventilation rate estimates based on the measured radiocarbon age difference between coexisting benthic and planktic foraminifera from glacial-age Pacific sediments. We also present new results from a series of eastern equatorial Pacific sediment cores. The conclusion is that the scatter in these results is so large that the apparent C-14 age of glacial deep Pacific water could lie anywhere between double and half today's. Further, it is not clear what is responsible for the wide scatter in the radiocarbon results.
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