What is the issue?

• Black carbon has a large effect on snow darkening and resultant melting of snow.
• Dust particles transported from as far as Saudi Arabia that gets deposited in the Western Himalayan Region — Hindu Kush, Karakoram and western Himalaya ranges — has a large role to play in melting of snow, particularly at higher elevations.
• This is the first time the role of long-distance transported dust in elevational heterogeneity of snow melting in the Himalayas has been made.
• While dust transported as elevated aerosol layers get deposited at 1-5 km elevation, black carbon emission is mostly a surface phenomenon and influences melting of snow from surface to about 3 km elevation.

Finding and Data

• Based on remote sensing data of spatial distribution of dust aerosol concentration over the Indian subcontinent and dust-induced snow albedo reduction over Himalayas during the period 2011-2016 (March-August) study showed impacts of dust and black carbon vary with surface elevation of snowpack.
• Though black carbon has a larger snow albedo darkening effect than dust due to a larger mass absorption efficiency, the radiative effects of dust deposited on snow are comparable to black carbon in the Western Himalayan Region at higher elevations.
• “As the elevation increases, the influence of dust becomes greater than black carbon.
• Black carbon mainly contributes to snowmelt at lower elevation while dust is the major contributor for snowmelt at higher elevation.

Contribution of Geographical Phenomenas

• Westerlies transport dust particles as elevated aerosol layers at maximum intensities mostly during the pre-monsoon period (March to May) and this gets deposited at higher elevations in the western Himalayan region.
• “Due to global warming, snow cover at lower elevations in the Himalayas will occur less frequently or totally disappear compared with snow cover at higher elevations.

Probable consequences:

• “Snowmelt is the main source of water for many major Himalayan rivers. Dust deposition during the pre-monsoon period causes early snowmelt water in the Himalayan rivers and a reduction of snowmelt water during peak summer months,”

https://www.thehindu.com/sci-tech/science/dust-responsible-for-snowmelt-at-higher-elevation-in-western-himalayan-region-study-says/article32779522.ece?homepage=true

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