Possible sources of carbon that may have caused global warming at the Paleocene-Eocene boundary are constrained using an intermediate complexity Earth-system model configured with early Eocene paleogeography. We find that 6800 Pg C (δ¹³C of –22‰) is the smallest pulse modeled here to reasonably reproduce observations of the extent of seafloor CaCO₃ dissolution. This pulse could not have been solely the result of methane hydrate destabilization, suggesting that additional sources of CO₂ such as volcanic CO₂, the oxidation of sedimentary organic carbon, or thermogenic methane must also have contributed. Observed contrasts in dissolution intensity between Atlantic and Pacific sites are reproduced in the model by reducing bioturbation in the Atlantic during the event, simulating a potential consequence of the spread of low-oxygen bottom waters.