Carnobacterium pleistocenium and Pithovirus sibericum both demonstrate that the possibility that virii and bacteria could survive being frozen for 300 centuries or more. There is the possibility of unique life-forms from Lake Vostok and Blood Falls.
In addition, there could be issues concerning toxic chemical/radioactive releases from artificial artifacts under ice such as may eventually happen when melting exposes project iceworm, a network of tunnels in the greenland icecap originally meant as a series of mobile nuclear ballistic missile launch sites.https://en.wikipedia.org/wiki/Project_Iceworm
hmmm.... how about a government research center as in 'andromeda strain' built into antarctic ice if biological weapons had taken the forefront over nuclear weapons during the cold war on earth?
Besides, weird things exposed after being thawed out of a block of ice has been a popular sci-fi trope for decades.
seems like fodder for a game or background to me.