What is cryoconite?

Cryoconite is powdery windblown dust made of a combination of small rock particles, soot and microbes which is deposited and builds up on snow, glaciers, or ice caps. The darkening, especially from small amounts of soot, absorbs solar radiation melting the snow or ice beneath the deposit, and sometimes creating a cryoconite hole. 

Cryoconite holes are water-filled cylindrical melt-holes on glacial ice surface. It has been reported from glaciers in many parts of the world: Arctic, Antarctic, Greenland, Canada, Tibet, and Himalayas. Cryoconite may contain dust from far away continental deserts or farmland, particles from volcanic eruptions or power plant emissions, and soot. 

It was first described and named by Nils AE Nordenskiöld when he travelled on Greenland's icecap in 1870. During summer, cryoconite holes frequently contain liquid water and thus provide a niche for cold-adapted microorganisms like bacteria, algae and animals like rotifers and tardigrades to thrive. 

Cryoconite typically settles and concentrates at the bottom of these holes creating a noticeable dark mass. Soot decreases the reflectivity, or albedo of ice, increasing absorption of heat. Cryoconite is constantly being added to snow and ice formations along with snow. It is buried within the snow or ice, but as the snow or ice melts increasing amounts of dark material is exposed on the surface, accelerating melting.

As the cryoconite absorbs solar radiation and promotes melting of the ice beneath it, the cylindrical holes are formed.  They have been suggested to play important roles in the glacier ecosystems because many kinds of living organisms have been reported from this structure on the glaciers, for example, algae, rotifer, tardigrada, insects and ice worm. Wharton in 1985 suggested that cryoconite holes are individual ecosystems with distinct boundaries, energy flow, and nutrient cycling.

 Cryoconite holes of Himalayan glaciers were also reported to provide semi-stagnant aquatic habitats to various organisms on the glacier such as algae, insects and copepods. Thus, it is important to know the basic characteristics of Himalayan cryoconite holes, such as morphology, distribution, and stability, to understand the glacier ecosystem of this region.