You have a few options.
With such little negative equity, it is likely that rental income would cover the interest and probably the full mortgage payment. So you may well have a profitable investment. How much is the house worth now? Would it be worth holding onto to hope that price rises might eliminate the negative equity?
If you have a cheap tracker mortgage, it's possible that the bank would do a deal with you if you told them you were emigrating. Unfortunately, they are not really geared up to such deals, so they might not.
You could sell the house, but you would still owe them the shortfall of €30k. In practice, they probably won't bother chasing it, but it will lie there for some years.
Or you could hand back the keys. They will sell the house and the shortfall will be a lot higher. Probably doesn't make that much difference.