I read a book, How to Clone a Mammoth, by ancient DNA researcher Beth Shapiro.

If what she wrote holds true deep in these glaciers (which take a long time to form so they presumably weren't always buried so deep), then the answer to what the risk may be is "very remote". DNA and RNA disintegrates into very small tatters pretty easily, turns out, frustrating the reconstruction of ancient genomes. Bacteria are definitely dead on multiple counts and viruses will be shredded.