Climate change implications for the glaciers of the Hindu Kush, Karakoram and Himalayan region

A J Wiltshire

doi:10.5194/tc-8-941-2014

Abstract

Abstract. The Hindu Kush, Karakoram, and Himalaya (HKH) region has a negative average glacial mass balance for the present day despite anomalous possible gains in the Karakoram. However, changes in climate over the 21st century may influence the mass balance across the HKH. This study uses regional climate modelling to analyse the implications of unmitigated climate change on precipitation, snowfall, air temperature and accumulated positive degree days for the Hindu Kush (HK), Karakoram (KK), Jammu–Kashmir (JK), Himachal Pradesh and West Nepal regions (HP), and East Nepal and Bhutan (NB). The analysis focuses on the climate drivers of change rather than the glaciological response. Presented is a complex regional pattern of climate change, with a possible increase in snowfall over the western HKH and decreases in the east. Accumulated degree days are less spatially variable than precipitation and show an increase in potential ablation in all regions combined with increases in the length of the seasonal melt period. From the projected change in regional climate the possible implications for future glacier mass balance are inferred. Overall, within the modelling framework used here the eastern Himalayan glaciers (Nepal–Bhutan) are the most vulnerable to climate change due to the decreased snowfall and increased ablation associated with warming. The eastern glaciers are therefore projected to decline over the 21st Century despite increasing precipitation. The western glaciers (Hindu Kush, Karakoram) are expected to decline at a slower rate over the 21st century in response to unmitigated climate compared to the glaciers of the east. Importantly, regional climate change is highly uncertain, especially in important cryospheric drivers such as snowfall timing and amounts, which are poorly constrained by observations. Data are available from the author on request.

Highlights

The high mountains of South Asia covering the Hindu Kush, Karakoram and Himalaya (HKH) belt have been described as the “Water Tower of Asia” (Viviroli et al, 2007; Immerzeel et al, 2010) due to their important role in feeding the major rivers of South Asia
Over 1.4 billion people depend on water from the Indus, Ganges, Brahmaputra, Yangtze, and Yellow rivers (Moors et al, 2011; Immerzeel et al, 2010) which arise in the HKH and Tibetan plateau, the influence of glacier discharge will decrease with distance downstream and river flow will become more influenced by precipitation variability (Kaser et al, 2010)
A close analysis of precipitation over the HKH suggests that the regional climate model (RCM) has a wet bias at high elevations

Summary

Introduction

The high mountains of South Asia covering the Hindu Kush, Karakoram and Himalaya (HKH) belt have been described as the “Water Tower of Asia” (Viviroli et al, 2007; Immerzeel et al, 2010) due to their important role in feeding the major rivers of South Asia. Water resources are considered vulnerable in the region due to the important role of snow and ice in the hydrology of the region (Barnett et al, 2005). The Indus originates in the Tibetan plateau and carries melt water from the glaciated Karakoram and Jammu–Kashmir region to a highly populated region. Over 1.4 billion people depend on water from the Indus, Ganges, Brahmaputra, Yangtze, and Yellow rivers (Moors et al, 2011; Immerzeel et al, 2010) which arise in the HKH and Tibetan plateau (not considered here), the influence of glacier discharge will decrease with distance downstream and river flow will become more influenced by precipitation variability (Kaser et al, 2010).

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Conclusion