A benthic δ13C-based proxy for atmospheric pCO2 over the last 1.5 Myr

A high-resolution marine proxy for atmospheric pCO(2) is needed to clarify the phase lag between pCO(2) and marine climate proxies and to provide a record of orbital-scale pCO(2) variations before the oldest ice core measurement at 800 ka. Benthic delta C-13 data should record deep ocean carbon storage and, thus, atmospheric pCO(2). This study finds that a modified delta C-13 gradient between the deep Pacific and intermediate North Atlantic (Delta delta C-13(P-NA/2)) correlates well with pCO(2). Delta delta C-13(P-NA/2) reproduces characteristic differences between pCO(2) and ice volume during Late Pleistocene glaciations and indicates that pCO(2) usually leads terminations by 0.2-3.7 kyr but lags by 3-10 kyr during two failed terminations at 535 and 745 ka. Delta delta 13C(P-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 pCO(2) of the last 1.5 Myr is estimated to be 155 ppm at similar to 920 ka. Citation: Lisiecki, L. E. (2010), A benthic delta C-13-based proxy for atmospheric pCO(2) over the last 1.5 Myr, Geophys. Res. Lett., 37, L21708, doi: 10.1029/2010GL045109.