The phrase "ice lenses" refers to lenses made of ice. It means that a small, curved piece of ice acts as a lens, just like the lens in eyeglasses or cameras, to focus or magnify light. Full definition
The lack of ice lenses is also crucial to having a constant snow density. (nichols.edu)
This is important information regarding the 1998 mass balance, because 7 - 11 % of the retained annual accumulation is typically in ice lenses. (nichols.edu)
«Very rarely ice lenses form directly beneath the kurgans,» explains Caspari. (sciencedaily.com)