Evaluating the glacial-deglacial carbon respiration and ventilation
change hypothesis as a mechanism for changing atmospheric CO2
Abstract
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
D14C was only ~50‰ lower during the
late glacial. Model simulations of the hypothesized ventilation change
during deglaciation lead to large increases in
d13CDIC, D14C and
ε14C that are not recorded in observations.