PICE seminar by Markus Jochum

Title: Carbon pools in a fully coupled LGM integration of CESM.

Jochum, Vettoretti, Nuterman & Chase

The Community Earth System Model (CESM) with marine and terrestrial biogeochemistry is configured to simulate the Last Glacial Maximum. A four thousand year long integration shows that atmospheric CO$_2$ concentration and ocean mean temperature match reconstructions. The sizes of the oceanic carbon pools are quantified and compared to their size in a preindustrial simulation. In agreement with previous studies it is found that the solubility pump, the disequilibrium pump and the effects of increased dust fluxes are of similar importance in explaining the simulated 70 ppm difference in CO$_2$. A surprising result is that the ocean in the glacial configuration contains less carbon than in its preindustrial simulation, because the soft tissue pump is significantly weaker. While the simulated differences to the carbon pools are consistent with reconstructions and all model parameters are the same in both configurations, several choices are made during the experimental design that are only poorly constrained by observations. Several sensitivity studies with CESM suggest that the sizes of inert carbon pools like ocean sediments and permafrost, and the energy available for diapycnal mixing are the most critical of these.