NOAA/WDS Paleoclimatology - Western Makassar Strait Radiocarbon, d18O and d13C Data During the Last 30 ka

The prevailing hypothesis to explain pCO2 rise at the last glacial termination calls upon enhanced ventilation of excess respired carbon that accumulated in the deep sea during the glacial. Recent studies argue lower [O2] in the glacial ocean is indicative of increased carbon respiration. The magnitude of [O2] depletion was 100-140µmol/kg at the glacial maximum. Because respiration is coupled to d13C of dissolved inorganic carbon (DIC), [O2] depletion of 100-140µmol/kg from carbon respiration would lower deep water d13CDIC by ~ 1‰ relative to surface water. Prolonged sequestration of respired carbon would also lower the amount of 14C in the deep sea. We show that Pacific Deep Water d13CDIC did not decrease relative to the surface ocean and ∆14C was only ~50‰ lower during the late glacial. Model simulations of the hypothesized ventilation change during deglaciation lead to large increases in d13CDIC, ∆14C and 14C that are not recorded in observations.