Permafrost changes in the northern Tien Shan during the Holocene

The evolution of permafrost within the northern Tien Shan during the Holocene is described. It is based on the interpretation of a temperature curve obtained from a deep borehole in the Zhusalykezen mountain pass (3336 m ASL), located in the Zailiysky Alatau Range. This curve indicates a zone where the temperature falls as the depth increases. Such an anomaly reflects past thermal conditions in the high mountains. At present, permafrost is absent on the southern slope where the borehole was drilled. Analysis of the temperature curve indicates that warming and cooling took place during the Holocene. Maximum warming occurred about 7000-10,000 years ago when the ground temperature rose by approximately 0.5-1.5 °C. Maximum cooling was recorded in the last millennium, the ground temperature being lower than today by 1.0-1.5 °C. These fluctuations are corroborated by relict permafrost and palaeocryogenic structures © 1997 John Wiley & Sons, Ltd.