Separation of atmosphere-ocean-vegetation feedbacks and synergies for mid-Holocene climate

We determine both the impact of atmosphere-ocean and atmosphere-vegetation feedback, and their synergy on northern latitude climate in response to the orbitally-induced changes in mid-Holocene insolation. For this purpose, we present results of eight simulations using the general circulation model ECHAM5-MPIOM including the land surface scheme JSBACH with a dynamic vegetation module. The experimental set-up allows us to apply a factor-separation technique to isolate the contribution of dynamic Earth system components (atmosphere, atmosphere-ocean, atmosphere-vegetation, atmosphereocean-vegetation) to the total climate change signal. Moreover, in order to keep the definition of seasons consistent with insolation forcing, we define the seasons on an astronomical basis. Our results reveal that north of 40 degrees N atmosphere-vegetation feedback (maximum in spring of 0.08 degrees C) and synergistic effects (maximum in winter of 0.25 degrees C) are weaker than in previous studies. The most important modification of the orbital forcing is related to the atmosphere-ocean component (maximum in autumn of 0.78 degrees C). Citation: Otto, J., T. Raddatz, M. Claussen, V. Brovkin, and V. Gayler (2009), Separation of atmosphereoceanvegetation feedbacks and synergies for mid-Holocene climate, Geophys. Res. Lett., 36, L09701, doi:10.1029/2009GL037482.