Originally Posted by Linda Sohl
If you'd like to try a set of experiments that are modifications of the Ice Age run (tweaking only one input at a time at first for clarity, then combinations of forcings), the best way to start it is to duplicate the Ice_Age_21_kya run, and select "All folders" as the Input folder option in the Input Files section of Setup Simulations. You can then change the Ocean surface file option to O8X10.250MLD in the Ocean Model section to use modern SSTs with the Ice Age setup. Greenhouse gas changes can of course just be set in the forcings section as desired, and there are also orbital parameters that you can modify if you wish. Since specified SST runs finish pretty quickly, you can easily do a number of different permutations to see what forcings appear to have the biggest effect on the variables you analyze.
If one use the file O8X10.250MLD, then one CANNOT study the effects of topology and vegatation on the Ice Age's climate. This is because the much warmer sea surface temperture SST will COMPLETELY dominate the simulation. For example, the surface air temperature will increase quite a lot to match the unchanged specified SST no matter the values the other forcings (within physically reasonable values). Furthermore, the simulation result may not physical because there may be unphysical interactions created due to the very large differences between the initial surface air temperature and SST.
Hence, starting with the Ice Age run, one MUST NOT change the ocean surface file if one want to compare the results between the Ice Age run and the modified simulation run.