Open Question: How to handle a loss on a house?

Just as a for instance...my husband and I are moving to Florida. We owe $200,000 on our house but can only sell it for $180,000. Renting is not an option and we have to face the $20,000 loss. We want to purchase a home in Florida. What happens to that $20,000 loss? Can we roll it into the new mortgage? Would we have to get a personal loan to pay it off? What about handling the loss when it comes to filing our taxes? Any help is much appreciated!