Climatic and Hydrologic Changes in the Tien Shan, Central Asia

Abstract

The authors analyze climatic and hydrologic data from 110 sites collected from the middle of the twentieth century to the present in the Tien Shan, one of the largest mountain systems of central Asia. In spite of a few confounding interregional variations in the temporal changes of surface air temperature, precipitation, runoff, glacier mass, and snow thickness in the Tien Shan, it has been possible to establish statistically significant longterm trends in these key hydroclimatic variables. The average rise in air temperature was 0.01ЊC yr Ϫ1 over the range, with slightly lower values below 2000-m elevation. The precipitation in the Tien Shan increased 1.2 mm yr Ϫ1 over the past half-century. The precipitation increase is larger at low altitudes in the northern and western regions than at altitudes above 2000 m. A decrease in snow resources occurred almost everywhere in the Tien Shan; the maximum snow thickness and snow duration have decreased on average 10 cm and 9 days, respectively. The annual runoff has dropped or did not change significantly in Tien Shan rivers. The main factor determining the change in river runoff is the type of precipitation (liquid or solid). Over the last few decades, periods of glacier decline have coincided with declining river runoff.

Recent climate trends on the northern slopes of the Tianshan Mountains, Xinjiang, China

“…Recent concerns about regional climate change have focused attention on the dependence of climate variables on elevation (Beniston and Rebetez 1996;Aizen et al 1997;Shrestha et al 1999;Liu and Chen 2000;Marchenko 1999;Giese and Moβig 2004;Bolch 2007). As far as the increasing rates of dependence of temperature on elevation is concerned, there are many contrasting results in the different mountainous regions.…”

“…As far as the increasing rates of dependence of temperature on elevation is concerned, there are many contrasting results in the different mountainous regions. In some mountainous regions, there is increased warming with increasing elevation (Beniston and Rebetez 1996;Aizen et al 1997;Shrestha et al 1999;Liu and Chen 2000). In contrast, some studies have shown that the rates of increase in temperature in the high elevation regions are lower than those in the low elevation regions (Marchenko 1999;Giese and Moβig 2004;Bolch 2007).…”

“…Its major peaks stand high over 4000-6000 m, with the highest one of 7439 m above sea level, and the deepest intermountain depression is 150 m below sea level. The Tianshan Mountains, the first mountain barrier facing northern air masses moving to central Asia, play an important role in determining the climatic processes occurring in northern central Asia (Aizen et al 1997). …”

Climatic imprint of the mid-latitude Westerlies in the Central Tian Shan of Kyrgyzstan and teleconnections to North Atlantic climate variability during the last 6000 years

“…Lake water temperature ranges between ~16°C in summer and 0-2°C in winter (ice cover usually between October and late April) with almost no vertical variations (<2°C) throughout the water column ( Figure 2b and c). The precipitation regime in the Kyrgyz Tian Shan is presently mainly controlled by the interaction between the Siberian Anticyclone and the mid-latitude Westerlies (Aizen et al, 1997), the latter bringing moisture from the Aral-Caspian Basin, the Mediterranean, the Black Sea, and the North Atlantic (Aizen et al, 2006). In contrast, the Asian summer monsoon does not directly influence the region at present and most likely had only negligible impact since the Mid-Holocene (Cheng et al, 2012).…”

Ecology and subsistence at the Mesolithic and Bronze Age site of Aigyrzhal-2, Naryn valley, Kyrgyzstan

“…The predominant wind directions today are from the west and result from the Westerly Jet Stream (Yang et al, 2013) but these are affected by seasonal influences from southern monsoon currents (Cour et al, 1999). The principal factor determining the climatic regimes of the Tian Shan Mountains is the interaction between the southwestern branch of the Siberian anticyclonic circulation and cyclonic activity from the west (Aizen et al, 1997). The high elevation is the main factor influencing the air temperature distribution at a macro scale (Mathis et al, 2014).…”