Abstract
Abstract. Glaciers in High Mountain Asia (HMA) provide an important water resource for communities downstream, and they are markedly impacted by global warming, yet there is a lack of understanding of the observed glacier mass balances and their spatial variability. In particular, the glaciers in the western Kunlun Shan and Karakoram (WKSK) ranges show neutral to positive mass balances despite global warming. Using models of the regional climate and glacier mass balance, we reproduce the observed patterns of glacier mass balance in High Mountain Asia of the last decades within uncertainties. We show that low temperature sensitivities of glaciers and an increase in snowfall, for a large part caused by increases in evapotranspiration from irrigated agriculture, result in positive mass balances in the WKSK. The pattern of mass balances in High Mountain Asia can thus be understood from the combination of changes in climatic forcing and glacier properties, with an important role for irrigated agriculture.
Highlights
Glaciers in High Mountain Asia (HMA; see Fig. 1) show a very diverse response to the changing climate
Different types of precipitation datasets seem to greatly underestimate the precipitation in mountainous terrain (Immerzeel et al, 2015; Ménégoz et al, 2013; Palazzi et al, 2013). These complications imply that any meteorological dataset, including reanalysis datasets, are associated with relatively large fundamental errors in the western Kunlun Shan and Karakoram (WKSK), which prevents reliable validation of any model of the WKSK, such as the one presented here
Not covering the glacierized areas of interest, we compared our Weather Research and Forecasting (WRF) output with data of the region surrounding the WKSK to ensure that the WRF output is a reasonable representation of the regional climate between 1980 and 2010
Summary
Glaciers in High Mountain Asia (HMA; see Fig. 1) show a very diverse response to the changing climate. Suggested causes of the Karakoram anomaly include an increase in winter snowfall (Cannon et al, 2015; Kapnick et al, 2014; Norris et al, 2015, 2018), summertime cooling (Bocchiola and Diolaiuti, 2013; Forsythe et al, 2017; Fowler and Archer, 2006; Khattak et al, 2011; Ul Hasson et al, 2017), and an increase in summertime precipitation and clouds due to irrigation in the agricultural regions adjacent to the Kunlun Shan and Pamir (de Kok et al, 2018) These hypotheses have only tried to explain the Karakoram anomaly in qualitative terms, identifying possible climatic conditions that could lead to glacier growth. We simulate glacier mass balances using modelled time series of temperature and snowfall from a regional climate model to reproduce the pattern of observed mass balances in HMA and to more deeply understand the underlying causes
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