Albedo (whiteness) & Dark Snow in Greenland, Asia and North America

September 19, 2014 @ EcoNews (Greek) & National Geographic (English)

black snow

Έχει σκουρύνει το χρώμα του χιονιού που πέφτει στη Γροιλανδία σύμφωνα με παρατηρήσεις της Γεωλογικής Υπηρεσίας της Δανίας. Αιτίες για αυτό είναι η μείωση της συχνότητας εκδήλωσης καταιγίδων κατά τη θερινή περίοδο, καθώς και η εμφάνιση μικροβίων και αιθάλης από πυρκαγιές δασών.

Περισσότερα στο Eco News

From Greenland’s ice sheets to Himalayan glaciers and the snowpacks of western North America, layers of dust and soot are darkening the color of glaciers and snowpacks, causing them to absorb more solar heat and melt more quickly, and earlier in spring. This trend toward darker snow from soot and dirt has been observed for years.

Albedo, or “whiteness,” is a scientific term meaning reflectivity. It is the fraction of solar energy that Earth reflects back into space. Lighter colored areas of Earth—those covered in new snow and ice—reflect most solar energy back into space. Darker areas of Earth—oceans, forests, and cities—absorb more solar heat. This whiteness is why snow-covered areas can stay cold, while dark spots like pavement and black roofs heat up. So when the white color of snow and ice is darkened by dirt and soot, more of the sun’s heat is absorbed, and snow and ice melt faster.

It’s not just Greenland and Arctic ice caps being affected by soot and dust. Atmospheric dirt is changing Himalayan glaciers in Asia and snowpacks in the mountains of western North America. Studies show cooking stoves that burn dung and wood darken snowpacks and ice in the Tibetan Plateau of the Himalayas. Soot from these biomass stoves falls on and darkens snow and ice in this region, whose extensive glaciers give birth to Asia’s largest rivers—the Yangtze, Yellow, Mekong, and Ganges—and provide water for two billion people.

Read more at National Geographic


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