If the melting polar icecaps are flooding the oceans with fresh water why don't we build desaulination plants?

If we remove the salt from the excess ocean water and put the salt back into the ocean would it not cancel each other out? Plus all the fresh water that could be made could help in times of drought. In foreign lands where water is scarce it could be a life saver. There by delaying the cool down of the oceans and reducing the land consumed by the raising levels. This would not stop the melting polar ice caps but it would buy so more time to clean up our act.