The Himalayas—which began forming about 50 million years ago
when the Indian subcontinent started to collide with Eurasia—are arguably the
world’s best-known snow-capped mountain range. But just to the north, beyond
the Tarim Basin, the same tectonic forces that built
the Himalayas also produced the Tien Shan, a similarly vast range of
snow-capped peaks that extends 2,500 kilometers (1,500 miles) through
Uzbekistan, Tajikistan, Kyrgyzstan, Kazakhstan, and western China.
The Moderate Resolution Imaging
Spectroradiometer (MODIS)
instrument on NASA’s Terra satellite acquired this view of the
sprawling range on October 9, 2012. It shows glacial ice with a layer of fresh
snow covering the ice in many areas. (See this MODIS image from August 31, 2012, to see the same
area with less snow.)
Geographers
usually divide the Tien Shan into western, northern, central, and easterm
ranges. The western and northern ranges have a milder and relatively moist
climate, while the central and eastern ranges have a more severe climate,
characterized by frigid winters and searing summers.
Many
parts of the Tien Shan are cold enough to sustain glaciers. Some of the highest
peaks and largest glaciers are clustered in the central range east of Lake Issyk-Kul, the large salt lake near the center of
the image. Although the lake is surrounded by snow-capped mountains and
situated at a high altitude, it does not generally freeze because of its high
salinity.
Tien
Shan’s glaciers play a crucial role in Central Asia’s hydrological cycle. An
estimated 15 percent of freshwater runoff in Kyrgyzstan comes from glaciers,
and the contribution can be much higher during the melting season, according to
an analysis published in October 2012.
In
the summer especially, cities such as Almaty, Bishkek, Tashkent, and Ürümqi
rely heavily on freshwater from glaciers for irrigation and for household
consumption, according to Annina Sorg, the Bern University researcher and
lead author of the 2012 paper. Based on a review of numerous studies, she
concluded that Tien Shan’s glaciers have retreated in recent decades due to
changing climate conditions.
· References
· Sorg, A. (2012, July 29) Climate change impacts on
glaciers and runoff in Tien Shan. Nature Climate Change.
· Eurekalert (2012, July 29) Researchers analyze melting
glaciers and water resources in Central Asia. Accessed Oct. 16, 2012.
· European Space Agency (2011, Dec. 9) Earth from space: bumpy borders. Accessed Oct. 16, 2012.
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