Simulating the Common Era and climate change scenarios with the MPI-ESM: opportunities for model-data comparison

The Max Planck Institute for Meteorology Earth System Model (MPI-ESM) is used to produce an ensemble of simulations of the Common Era (CE) and several climate change scenarios until 2300 CE. The ensemble of simulations uses the standard version of the MPI-ESM (MPI-ESM1.2-LR) and a variant that includes developments in the hydrology and thermodynamics of its land surface model, JSBACH, particularly over permafrost areas: the Permafrost Physics Ensemble (MPIESM-PePE). Five members of the ensemble extend back to 0 CE under reference PMIP4/CMIP6 forcing specifications.

Subsurface hydro-thermodynamic processes have been modified to allow for exploring uncertainties related to the land model depth and to Arctic climate, specifically Arctic hydrology. Different vertical discretizations of JSBACH, including changes in its depth, are considered to modify the thermodynamic configuration of the model. JSBACH was modified to also include soil moisture phase changes with freezing-thaw conditions and other hydrological features, like an organic topsoil layer; dynamic soil thermal properties, or the implementation of a simple wetland and a new multi-layer snow scheme. These hydrological changes result in three contrasting model configurations: one stemming from the use of the standard model and two different set ups, including the previous improvements, in which the Arctic becomes comparatively wetter or drier.

Changes in a wetter or drier Arctic hydrology feedback to change Arctic temperatures and Arctic Amplification within periods of warming/cooling and thereby influencing Northern Hemispheric circulation. Changes in land depth influence the subsurface thermal state, with implications for land energy storage and permafrost. The MPIESM-PePe ensemble allows for exploring sensitivity to these changes in multi-centennial to millennial timescales. Some examples of model-data comparison will be provided.