Evaluating the Glacial-Deglacial Carbon Respiration and Ventilation Change Hypothesis as a Mechanism for Changing Atmospheric CO2

Abstract

The prevailing hypothesis to explain pCO(2) 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 [O-2] in the glacial ocean is indicative of increased carbon respiration. The magnitude of [O-2] depletion was 100-140 mu mol/kg at the glacial maximum. Because respiration is coupled to delta C-13 of dissolved inorganic carbon (DIC), [O-2] depletion of 100-140 mu mol/kg from carbon respiration would lower deep water delta C-13(DIC) by similar to 1 parts per thousand relative to surface water. Prolonged sequestration of respired carbon would also lower the amount of C-14 in the deep sea. We show that Pacific Deep Water delta C-13(DIC) did not decrease relative to the surface ocean and Delta C-14 was only similar to 50 parts per thousand lower during the late glacial. Model simulations of the hypothesized ventilation change during deglaciation lead to large increases in delta C-13(DIC), Delta C-14, and epsilon C-14 that are not recorded in observations.