Abstract
Summary The accurate quantification of current and past Himalayan glacier mass budgets is vital if we are to understand the evolution of the Asian water tower, which provides water to the planet’s most populous region. In this work, we generated a geodetic time series spanning six decades over 79 glaciers surrounding Mt. Everest and found consistent acceleration of glacier mass loss between the 1960s (−0.23 ± 0.12 mwe a−1) and the modern era (−0.38 ± 0.11 mwe a−1 from 2009 to 2018). Glacier mass loss has varied depending on glacier terminus type and surface characteristics, and glacier thinning is now occurring at extreme altitudes (>6,000 masl). Our time series also captures the first documented surge of a glacier in the Mt. Everest region. These multi-decadal observations of glacier mass loss form a baseline dataset against which physically based glacier evolution models could be calibrated before they are used for predicting future meltwater yield.
Highlights
We significantly extend the work by Bolch et al.[18,27] to produce the longest possible geodetic time series of glacier surface elevation change in the Everest region on both the north and south sides of the main orographic divide and glaciers to the east of Mt
We have compiled geodetic datasets derived from declassified Corona KH-4 (1962), Corona KH-4B (1969), and Hexagon KH-9 (1976) imagery, aerial photographic surveys (1984 and 1992), and satellite imagery acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER; 2001), Cartosat (2009 and 2018), and PlanetScope (2017) sensors over the regional extent of the National Geographic survey from 1984 (Figures 1 and 2), which we slightly extend to cover glacier extent fully (e.g., Kangshung and Barun Glaciers)
We examine the rate of ice loss over nearly 60 years across seven quasi-decadal time steps
Summary
Glacier meltwater originating from the Hindu Kush Himalaya sustains the flow of some of south Asia’s largest rivers, on which more than 230 million people living in the mountains and hills of the region and, to a lesser extent, people living in the lowlands depend for their water supply.[1,2] In the face of climate change, the contribution of these glaciers to river flow will become increasingly important as drought intensity and duration increase in the coming decades.[3,4,5] glaciers in the Himalaya are shrinking,[6] and their contribution to downstream river flow will become unsustainable in the future.[7,8] The accurate quantification of the current and historical rate of glacier melt is vital if the timing and magnitude of future meltwater yield are to be constrained by the projections of glacier evolution models.The mass loss of individual glaciers can be monitored by field measurements of glacier accumulation and ablation, the difference between which determines a glacier’s mass balance.[9,10] In situ measurements of glacier mass balance take place at a few benchmark glaciers across high-mountain Asia (HMA),[6,11] but such measurements are logistically difficult, and the application of this method is not possible at a regional scale. Glacier meltwater originating from the Hindu Kush Himalaya sustains the flow of some of south Asia’s largest rivers, on which more than 230 million people living in the mountains and hills of the region and, to a lesser extent, people living in the lowlands depend for their water supply.[1,2] In the face of climate change, the contribution of these glaciers to river flow will become increasingly important as drought intensity and duration increase in the coming decades.[3,4,5] glaciers in the Himalaya are shrinking,[6] and their contribution to downstream river flow will become unsustainable in the future.[7,8] The accurate quantification of the current and historical rate of glacier melt is vital if the timing and magnitude of future meltwater yield are to be constrained by the projections of glacier evolution models. The use of laser altimetry data, interferometric synthetic aperture radar (InSAR) data, and stereo satellite imagery to generate digital elevation models (DEMs), which can be analyzed to derive the rates of glacier surface elevation change, is the most practical way to examine geodetic glacier mass balance over
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