CESM 1.0.2 Near Past Initial Conditions User Guide: Prescribing Ice Sheets

Abstract

The Community Earth System Model has been developed and is maintained by NCAR. At this stage of the report, the CESM 1.0.2 includes atmosphere, land, ocean, sea-ice and a partially coupled ice sheets model. Several grid resolutions have been developed for each component and for present-day Earth’s topography/bathymetry and one of the big advantage of this model is that the running procedure is straightforward in its present-day configuration for any new user. However, the CESM 1.0.2 components are not flexible to simulate near or deep past climates which require a different topography/bathymetry relative to present-day. Indeed, to simulate a different continental distribution and a different sea level, each component needs substantial changes in its initial conditions files which require an advanced knowledge of the model. In order to make those kind of changes accessible for new users, the following document aims at proposing a relatively simple procedure to modify the initial conditions files for the coupled atmosphere-land-ocean-sea-ice compset of the CESM 1.0.2 (B compset). This procedure was mainly developed at NCAR but never tested before on the different supercomputing platforms and outside of NCAR. The guide presented here have been successfully tested on CMCC IBM Power 6 platform taking as example a glaciation configuration. However, this process is by far non automatic and requires some substantial manual work at each stage of the procedure. Finally, following this procedure does not provide any guarantees that the simulations will be successful.We thank Nan Rosembloom and Bette Otto-Bliesner for their technical and scientific support to learn the procedure described in this guide. The research leading to these results has received funding from the Italian Ministry of Education, University and Research and the Italian Ministry of Environment, Land and Sea under the GEMINA project.