I am setting up some CORDEX runs and have a question about sea ice in RegCM-4.4rc8.

Several of the CORDEX domains have coverage by sea ice.  However there is no sea ice file for the ERA-Interim data. 

Can someone give advice on how to include sea ice when using ERA-Interim for ic/bc?  For physical consistency I would strongly prefer to use sea ice from ERA-Interim itself, but apparently this is not an option. (It is possible I will code it up if I have time.) However I am willing to consider other approaches.