Deglaciation-enhanced mantle CO₂ fluxes at Yellowstone imply positive climate feedback

Mantle melt generation in response to glacial unloading has been linked to enhanced magmatic volatile release in Iceland and global eruptive records. It is unclear whether this process is important in systems lacking evidence of enhanced eruptions. The deglaciation of the Yellowstone ice cap did not observably enhance volcanism, yet Yellowstone emits large volumes of CO₂ due to melt crystallization at depth. Here we model mantle melting and CO₂ release during the deglaciation of Yellowstone (using Iceland as a benchmark). We find mantle melting is enhanced 19-fold during deglaciation, generating an additional 250-620 km³. These melts segregate an additional 18-79 Gt of CO₂ from the mantle, representing a ~3-15% increase in the global volcanic CO₂ flux (if degassed immediately). We suggest deglaciation-enhanced mantle melting is important in continental settings with partially molten mantle - including Greenland and West Antarctica - potentially implying positive feedbacks between deglaciation and climate warming.