Annals of Glaciology, 34, 409-414.
Optical characteristics of cryoconite (surface dust) on glaciers: the relationship between light absorbency and the property of organic matter contained in the cryoconite.
Frontier Observational Research System for Global Change, International Arctic Research Center, University of Alaska Fairbanks, 930 Koyukuk Dr. P.O.Box 757335 Fairbanks AK 99775-7335 U.S.A.
Optical characteristics of the cryoconite collected from nine glaciers in the Himalayas, Tibet, and the Arctic (Canada and Svalbard) were analyzed. The spectral light reflectance (visible region) of the cryoconite on six glaciers in the Arctic and the Himalayas was generally low, indicating high light absorbency (dark-coloration) of the cryoconite. In contrast, the spectral albedos of the cryoconite on three glaciers in Tibet were significantly higher than that of the other glaciers. There was no significant difference in spectral reflectance of mineral particles contained in the cryoconite between the Tibetan and the other glaciers, indicating that the difference in the albedo of the cryoconites is not due to the mineral particles, but due to organic matter contained in the cryoconite. Chemical analysis of the organic matter in the cryoconites revealed that the light absorbency of cryoconites is due to the amount of humic substances, which are dark-colored organic substances, the residue of bacterial decomposition of organic matter. The cryoconite of the three glaciers in Tibet contained significantly smaller amounts of humic substances than the other glaciers. The small amount on the Tibetan glaciers is probably due to different biological or chemical conditions than the other glaciers. Results show that the formation of the humic substances in the cryoconite affect its optical characteristics, and possibly affect the surface albedo of the glaciers.