You seem to have a very casual approach there. Life would take the mother of all blows from a rapid melting. The continents' shores are polluted enough that it would wipe off most of the shallow water marine life. Species are NOT trained to such a rapid change.
A lot of species died in the climate change periods of the holocen, and they were not nearly as rapid as what is projected. But also, species had a much larger and undamaged habitat then. And the shores were clean. Finally, there was no dominant species to kill all animals bigger than a grasshoper because it was starving from the huge reduction of its agricultural land.

It would be an unfathomable catastrophe.

Now, I don't expect +70m anytime soon, and by that I mean within the next million years. It would be too catastrophic not to take the most drastic of actions.

Earth provides enough to satisfy every man's need, but not every man's greed. Gandhi