Changing atmospheric <supscr>14</supscr>C and the record of deep water paleoventilation ages

We propose a new calculation method to better estimate the deep water ventilation age from benthic-planktonic foraminifera 14C ages. Our study is motivated by the fact that changes in atmospheric A14C through time can cause contemporary benthic and planktonic foraminifera to have different initial A14C values. This effect can cause spurious ventilation age changes tobe interpreted from the geologic data. Using a new calculation method, 14C projection ages, we recalculate the data from the Pacific Ocean. Contrary to previous results, we find that the Pacific intermediate and deep waters were about 600 years older than today at the last glacial maximum. In addition, there are possible signals of ventilation age change prior to ice sheet melting and at the Younger Dryas. However, the data are still too sparse to constrain these ventilation transients.