Abstract
Abstract. Few glaciological field data are available on glaciers in the Hindu Kush–Karakoram–Himalayan (HKH) region, and remote sensing data are thus critical for glacier studies in this region. The main objectives of this study are to document, using satellite images, the seasonal changes of surface albedo for two Himalayan glaciers, Chhota Shigri Glacier (Himachal Pradesh, India) and Mera Glacier (Everest region, Nepal), and to reconstruct the annual mass balance of these glaciers based on the albedo data. Albedo is retrieved from Moderate Resolution Imaging Spectroradiometer (MODIS) images, and evaluated using ground based measurements. At both sites, we find high coefficients of determination between annual minimum albedo averaged over the glacier (AMAAG) and glacier-wide annual mass balance (Ba) measured with the glaciological method (R2 = 0.75). At Chhota Shigri Glacier, the relation between AMAAG found at the end of the ablation season and Ba suggests that AMAAG can be used as a proxy for the maximum snow line altitude or equilibrium line altitude (ELA) on winter-accumulation-type glaciers in the Himalayas. However, for the summer-accumulation-type Mera Glacier, our approach relied on the hypothesis that ELA information is preserved during the monsoon. At Mera Glacier, cloud obscuration and snow accumulation limits the detection of albedo during the monsoon, but snow redistribution and sublimation in the post-monsoon period allows for the calculation of AMAAG. Reconstructed Ba at Chhota Shigri Glacier agrees with mass balances previously reconstructed using a positive degree-day method. Reconstructed Ba at Mera Glacier is affected by heavy cloud cover during the monsoon, which systematically limited our ability to observe AMAAG at the end of the melting period. In addition, the relation between AMAAG and Ba is constrained over a shorter time period for Mera Glacier (6 years) than for Chhota Shigri Glacier (11 years). Thus the mass balance reconstruction is less robust for Mera Glacier than for Chhota Shigri Glacier. However our method shows promising results and may be used to reconstruct the annual mass balance of glaciers with contrasted seasonal cycles in the western part of the HKH mountain range since the early 2000s when MODIS images became available.
Highlights
800 million people rely directly on water originating from the high mountains of Asia for fresh water supply and hydropower (Immerzeel et al, 2010)
We compared the broadband albedo measured under clear sky conditions at the automatic weather stations (AWSs) with the BS albedo retrieved by MODImLab and MOD10 algorithm on the corresponding pixel for both glaciers (Fig. 5)
The limited number of albedo samples (n = for MODImLab and n = for MOD10) and the relatively small variance (σ = 0.05 for the AWS albedo used to compare with MOD10) on Chhota Shigri Glacier prevented a reliable conclusion about the quality of the albedo retrieval techniques (Fig. 5a)
Summary
800 million people rely directly on water originating from the high mountains of Asia for fresh water supply and hydropower (Immerzeel et al, 2010). F. Brun et al.: Surface albedo of Himalayan glaciers and links with mass balance (HKH) region (e.g., Immerzeel et al, 2013). Brun et al.: Surface albedo of Himalayan glaciers and links with mass balance (HKH) region (e.g., Immerzeel et al, 2013) These glaciers represent the largest glacierized area in the lower latitudes and are significant contributors to current and future sea level rise (Gardner et al, 2013; Radicet al., 2014). It is important to assess how these glaciers would respond to climate change, and what would be the consequences of their evolution in terms of glacial hazards and modification of local and regional hydrology (e.g., Richardson and Reynolds, 2000; Kaser et al, 2010)
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