Status and Change of the Cryosphere in the Extended Hindu Kush Himalaya Region

Bolch, Tobias; Shea, J. M.; Liu, Shiyin; Azam, Farooq; Gao, Yang; Gruber, Stephan; Immerzeel, Walter W.; Kulkarni, Anil V.; Li, Huilin; Tahir, Adnan Ahmad; Zhang, Guoqing; Zhang, Yinsheng

doi:10.1007/978-3-319-92288-1_7

Cited by 187 publications

(191 citation statements)

References 388 publications

(519 reference statements)

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“…Our results are generally consistent with other full-HMA glacier mass balance assessments, including the comprehensive review by Bolch et al (2019) and recent analysis by Brun et al (2017). Considering the range of methods, datasets, time periods and spatial coverage of previous studies, we limit our direct comparison with the "reference" analysis by Brun et al (2017) (similar methods, similar time period), and refer the reader to Brun et al (2017) for detailed comparisons with earlier work, and to Bolch et al (2019) for more complete context.…”

Section: Comparison With Previous Worksupporting

confidence: 85%

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A Systematic, Regional Assessment of High Mountain Asia Glacier Mass Balance

et al. 2020

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High-mountain Asia (HMA) constitutes the largest glacierized region outside of the Earth's polar regions. Although available observations are limited, long-term records indicate sustained HMA glacier mass loss since ∼1850, with accelerated loss in recent decades. Recent satellite data capture the spatial variability of this mass loss, but spatial resolution is coarse and some estimates for regional and HMA-wide mass loss disagree. To address these issues, we generated 5,797 high-resolution digital elevation models (DEMs) from available sub-meter commercial stereo imagery (DigitalGlobe WorldView-1/2/3 and GeoEye-1) acquired over HMA glaciers from 2007 to 2018 (primarily 2013-2017). We also reprocessed 28,278 ASTER DEMs over HMA from 2000 to 2018. We combined these observations to generate robust elevation change trend maps and geodetic mass balance estimates for 99% of HMA glaciers between 2000 and 2018. We estimate total HMA glacier mass change of −19.0 ± 2.5 Gt yr −1 (−0.19 ± 0.03 m w.e. yr −1 ). We document the spatial pattern of HMA glacier mass change with unprecedented detail, and present aggregated estimates for HMA glacierized sub-regions and hydrologic basins. Our results offer improved estimates for the HMA contribution to global sea level rise in recent decades with total cumulative sea-level rise contribution of ∼0.7 mm from exorheic basins between 2000 and 2018. We estimate that the range of excess glacier meltwater runoff due to negative glacier mass balance in each basin constitutes ∼12-53% of the total basin-specific glacier meltwater runoff. These results can be used for calibration and validation of glacier mass balance models, satellite gravimetry observations, and hydrologic models needed for present and future water resource management.

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Section: Comparison With Previous Worksupporting

confidence: 85%

“…These methods have inherent differences in sampling strategy, resolution, and sensitivity, which can lead to discrepancies in results. For detailed reviews of past work, we refer the reader to Bolch et al (2012), Farinotti et al (2015), Kääb et al (2015), Brun et al (2017), Azam et al (2018), and Bolch et al (2019).…”

Section: Introductionmentioning

confidence: 99%

A Systematic, Regional Assessment of High Mountain Asia Glacier Mass Balance

et al. 2020

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“…The Hindu Kush Himalayan (HKH) region (the 'third pole') covers 4.2 million km 2 and feeds the 10 largest river systems in Asia (Bajracharya et al, 2015), supplying ~1.4 billion people with water (Bolch et al, 2012;Immerzeel, Beek, & Bierkens, 2010). HKH warming rates are higher than the global average (Pachauri et al, 2014;Peng, Piao, Ciais, Fang, & Wang, 2010) and recent work concludes with high confidence that snow-covered areas and snow volumes will decrease across most HKH regions over coming decades, in response to climatic change (Bolch et al, 2019). For these reasons, most scientific work in the HKH region has focused on understanding the state and fate of glaciers (Bolch et al, 2012;Brun, Berthier, Wagnon, Kääb, & Treichler, 2017;Shannon et al, 2019), changes in glacial resources (Immerzeel et al, 2010;Kääb, Berthier, Nuth, Gardelle, & Arnaud, 2012;Kehrwald et al, 2008), hydrological risks (Shrestha et al, 2010;Worni, Huggel, & Stoffel, 2013) or monsoon-driven run-off dynamics (Armstrong et al, 2018;Thayyen, Gergan, & Dobhal, 2005).…”

Section: Introductionmentioning

confidence: 99%

Vegetation expansion in the subnival Hindu Kush Himalaya

Anderson

Fawcett

Anthony

et al. 2020

Global Change Biology

102

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The mountain systems of the Hindu Kush Himalaya (HKH) are changing rapidly due to climatic change, but an overlooked component is the subnival ecosystem (between the treeline and snow line), characterized by short‐stature plants and seasonal snow. Basic information about subnival vegetation distribution and rates of ecosystem change are not known, yet such information is needed to understand relationships between subnival ecology and water/carbon cycles. We show that HKH subnival ecosystems cover five to 15 times the area of permanent glaciers and snow, highlighting their eco‐hydrological importance. Using satellite data from the Landsat 5, 7 and 8 missions, we measured change in the spatial extent of subnival vegetation from 1993 to 2018. The Landsat surface reflectance‐derived Normalized Difference Vegetation Index product was thresholded at 0.1 to indicate the presence/absence of vegetation. Using this product, the strength and direction of time‐series trends in the green pixel fraction were measured within three regions of interest. We controlled for cloud cover, snow cover and evaluated the impact of sensor radiometric differences between Landsat 7 and Landsat 8. Using Google Earth Engine to expedite data processing tasks, we show that there has been a weakly positive increase in the extent of subnival vegetation since 1993. Strongest and most significant trends were found in the height region of 5,000–5,500 m a.s.l. across the HKH extent: R2 = .302, Kendall's τ = 0.424, p < .05, but this varied regionally, with height, and according to the sensors included in the time series. Positive trends at lower elevations occurred on steeper slopes whilst at higher elevations, flatter areas exhibited stronger trends. We validated our findings using online photographs. Subnival ecological changes have likely impacted HKH carbon and water cycles with impacts on millions of people living downstream, but the strength and direction of impacts of vegetation expansion remain unknown.

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“…There was a striking lack of data and research in the mountains in spite of their importance as the water towers of Asia. But, fortunately, over the last 10 years there have been robust scientific studies on the HKH cryosphere and its changes and subsequent impact downstream; these are synthesized in the HIMAP report (Bolch et al, 2019;Wester, Mishra, Mukherji, & Shrestha, 2019).…”

Section: Climate Changementioning

confidence: 99%

Scarcity of water or scarcity of management?

Molden

2019

International Journal of Water Resources Development

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This article investigates the relation between water scarcity and water management. There are many different perceptions of water scarcity, which can include the conditions of arid environments, a general lack of access to water, insufficient water at a basin scale, or difficulty in meeting competing needs. All these issues will intensify with greater consumption and climate change. Asit Biswas reminds us that the root cause of scarcity is the way water is managed. Following this wisdom, I examine different contexts of scarcity I have encountered in my work and reflect on the management challenges which drive and transform water scarcity. ARTICLE HISTORY

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Status and Change of the Cryosphere in the Extended Hindu Kush Himalaya Region

Cited by 187 publications

References 388 publications

A Systematic, Regional Assessment of High Mountain Asia Glacier Mass Balance

A Systematic, Regional Assessment of High Mountain Asia Glacier Mass Balance

Vegetation expansion in the subnival Hindu Kush Himalaya

Scarcity of water or scarcity of management?

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