Glaciers are not Sterile. 

Jemma Wadham, a professor at Bristol, has written a book, Ice Rivers, (ISBN-10 : 0241467683, ISBN-13 : 978-0241467688) which she introduces in THIS ARTICLE.

She has had a life long love of glaciers and seems to have visited all of them!

She writes about the microbes living in and beneath glaciers. Many live on the soil and other organic stuff below the ice, producing methane - the methanogens. But there are others which consume the methane - the methanotrophs. 

Fast flowing rivers emerging from melting glaciers are super-saturated with methane. No one knows how much methane is trapped in glaciers, some in solid  form as methane hydrate.