Impact of Recent Glacier Advance to Runoff of a Large Glacier-Fed River in China Karakoram

Abstract:

50% of glaciers in Karakoram experienced an abrupt advance, including surging, thickening and expanding since the mid-1990s. The water of Yarkant River in China Karakoram is mainly supplied by glaciers and snow meltwater, so runoff is greatly affected by air temperature. The meltwater flow has responded to both wetting and cooling climate and glacier changes in high mountains. The study analyzed the variations of climate, glaciers and summer meltwater flow in two different periods, glacier retreat and advance before and after 1996 based on long term data of monthly air temperature, precipitation and discharge from alpine stations for recent 53 years (1960-2012). The influence of the glacier and climatic conditions (retreat/advance vs temperature and precipitation) on runoff were simulated by a monthly regression model, through which we explored the hydrological changes in Yarkant River. By two groups of the monthly regression model, we found reliable correlations between monthly air temperature and discharge during June to September of strong ablation months in glacier retreat period before 1996. Then in the glacier advance, the melt coefficient of June discharge become into much greater than that of after 1996 in a warmer and wetter climate, and the coefficient in July did not change. However the correlationa disappeared in August and September with a cool and wet climate since 1997, the results indicated no increase in summer flow suggest that the glacier thickening, surging and expanding can intensify both meltwater storage and refreeze in subglacial systems.