Temporal and Spatial Changes of Permafrost in the Tien Shan Mountains Since the Little Ice Age.

Details Temporal and Spatial Changes of Permafrost in the Tien Shan Mountains Since the Little Ice Age. Temporal and Spatial Changes of Permafrost in the Tien Shan Mountains Since the Little Ice Age.

Dec 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufm.c51b0426m&link_type=abstract

American Geophysical Union, Fall Meeting 2006, abstract #C51B-0426

Other

0702 Permafrost (0475), 0706 Active Layer, 0768 Thermal Regime, 0772 Distribution, 0798 Modeling

Scientific paper

During the Late Holocene there were numerous periods of warming and cooling in the Tien Shan Mountains, Central Asia. Ground temperatures and permafrost area in the Tien Shan have been subjected to repeated fluctuations during the last millennia brought about by the general planetary changes in climate. The altitudinal oscillations of the mean annual air temperature (MAAT) zero Centigrade isotherm had a range of about 300 m during that time. Air temperature in the Tien Shan Mountains has increased at a higher rate than the global mean during the 20th century. Climate warming in the high-mountains regions could induce the further near-surface permafrost degradation, which may lead to slope instability and permafrost-related hazards. The main objectives of the modeling process were to estimate the permafrost thermal regime and assess the area where permafrost disappeared since the second part of the nineteenth century. To estimate the effect of climate change on permafrost a one-dimensional process-based model was used to simulate the ground thermal regime of the Tien Shan at a resolution of a half-degree latitude-longitude since the Little Ice Age up to present. The results of numerical simulation show that at an altitude of 2500 m a.s.l. the permafrost temporary formed at least three times during the last 500 years. At the lover altitudinal boundary of permafrost distribution the permafrost temperatures now are close to 0°C and at some sites permafrost degradation has already started. Analysis of measured active layer and permafrost temperatures coupled with numerical thermal modeling (permafrost temperature reanalysis) shows that most of the recently thawed permafrost was formed during the Little Ice Age. The modeling of alpine permafrost dynamics shows that the altitudinal lower boundary of permafrost distribution has shifted by about 150-200 m upward since the end of the Little Ice Age (circa 1850). During the same period, the area of permafrost distribution within Tien Shan could decrease approximately by 16%.

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