Abstract
Impacts of projected climate and glacier change on river discharge in five glacierized catchments in the northern Tien Shan, Kazakhstan are investigated using a conceptual hydrological model HBV-ETH. Regional climate model PRECIS driven by four different GCM-scenario combinations (HadGEM2.6, HadGEM8.5, A1B using HadCM3Q0 and ECHAM5) is used to develop climate projections. Future changes in glaciation are assessed using the Blatter–Pattyn type higher-order 3D coupled ice flow and mass balance model. All climate scenarios show statistically significant warming in the 21st Century. Neither projects statistically significant change in annual precipitation although HadGEM and HadCM3Q0-driven scenarios show 20–37% reduction in July–August precipitation in 2076–2095 in comparison with 1980–2005. Glaciers are projected to retreat rapidly until the 2050s and stabilize afterwards except under the HadGEM8.5 scenario where retreat continues. Glaciers are projected to lose 38–50% of their volume and 34–39% of their area. Total river discharge in July–August, is projected to decline in catchments with low (2–4%) glacierization by 20–37%. In catchments with high glacierization (16% and over), no significant changes in summer discharge are expected while spring discharge is projected to increase. In catchments with medium glacierization (10–12%), summer discharge is expected to decline under the less aggressive scenarios while flow is sustained under the most aggressive HadGEM8.5 scenario, which generates stronger melt.
Highlights
High mountains are often referred to as water towers of the world and this is true in Central Asia where snow and glacier melt nourishes rivers providing water to the arid plains and sustaining agricultural production on the irrigated land [1]
This paper presented projections of river discharge for five catchments in the northern Tien Shan with different specific discharge and glacierization varying between 2.6% in the Kaskelen catchment to 16% in the Ulken Almaty and Talgar catchments for four climate and glacier scenario-model combinations
The Tien Shan Mountains are water towers of Central Asia and the state of runoff generated in the mountains is of upmost importance to national economies and international relations in the region
Summary
High mountains are often referred to as water towers of the world and this is true in Central Asia where snow and glacier melt nourishes rivers providing water to the arid plains and sustaining agricultural production on the irrigated land [1]. Various components of the mountain cryosphere contribute to the formation of discharge including melting snow pack, glacier ice, permafrost and ice contained in rock glaciers [2]. All these components are affected by climate change. Observations suggest a decrease in the extent, depth, and duration of mountain snow pack [3]. There is ample evidence for declining glacier mass balance [4] and wastage of glaciers across the Tien Shan mountains [5,6,7,8,9,10]
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