A benthic δC‐based proxy for atmospheric pCO2 over the last 1.5 Myr

[1] A high‐resolution marine proxy for atmospheric pCO2 is needed to clarify the phase lag between pCO2 and marine climate proxies and to provide a record of orbital‐scale pCO2 variations before the oldest ice core measurement at 800 ka. Benthic dC data should record deep ocean carbon storage and, thus, atmospheric pCO2. This study finds that a modified dC gradient between the deep Pacific and intermediate North Atlantic (DdCP−NA 2 ) correlates well with pCO2. Dd CP−NA 2 reproduces characteristic differences between pCO2 and ice volume during Late Pleistocene glaciations and indicates that pCO2 usually leads terminations by 0.2–3.7 kyr but lags by 3–10 kyr during two “failed” terminations at 535 and 745 ka.DdCP−NA 2 gradually transitions from 41‐ to 100‐kyr cyclicity from 1.3–0.7 Ma but has no secular trend in mean or amplitude since 1.5 Ma. The minimum pCO2 of the last 1.5 Myr is estimated to be 155 ppm at ∼920 ka. Citation: Lisiecki, L. E. (2010), A benthic dC‐ based proxy for atmospheric pCO2 over the last 1.5 Myr, Geophys. Res. Lett., 37, L21708, doi:10.1029/2010GL045109.