cryoconite hole

plural cryoconite holes

1. a hollow or pond formed in a layer of snow or ice, commonly on the surface of a glacier or in polar regions, where a dark patch of cryoconite absorbs sunlight, generating heat so that it melts its way into the white, reflective ice.

   ...cryoconite holes, thick ice covered lakes, nunataks, and subglacial environments may have played a role as refuges for microorganisms and other biota during periods of glaciation and therefore favoured the development of endemic species.

   2006, Joseph Seckbach, Life as We Know It, →ISBN