I believe that God took the waters back off the earth, like He did in Genesis 1 to form the water canopy -- or possible giant ice cube in space, whatever shape it was.
Anyway, I believe that God took the waters back off the earth, including most of the waters from 'the fountains of the deep', along with some debris, and placed them elsewhere in our solar system, to serve as a "reminder" to other angels of what happened the year of the Flood.
Paul says that we entertain angels unaware, and that tells me that angels walk this earth incognito; and I would venture to say they have a cosmic reminder of what happened, just in case any of them get any ideas.
The dove that bringing back the olive leaf, tells me that God "hypergrew" the earth again, just as He did in Genesis 1 -- and that the earth was green once more.
Again, this is pure speculation on my part.