The title explains it all. Do objects suspended in ice sink over time? You may remember the story of World War 2 planes that were found 260 ft under the ice which would be anachronistic with seasonal ice layering alone. I'm trying to establish other possible mechanisms. I know that ice flows up and down in glaciers, but will an object actually sink in ice over time? 

Also, in what way would they sink? Would heavier parts sink faster than the lighter. Does buoyancy play a role.