Influence of Supraglacial Debris Thickness on Thermal Resistance of the Glaciers of Chandra Basin, Western Himalaya

Lavkush Kumar Patel,Bhanu Pratap,Sunil Oulkar,Meloth Thamban,Parmanand Sharma,Ajit Singh

doi:10.3389/feart.2021.706312

Lavkush Kumar Patel, Bhanu Pratap + Show 4 more

Open Access

https://doi.org/10.3389/feart.2021.706312

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Abstract

A large number of glaciers in the Hindu-Kush Himalaya are covered with debris in the lower part of the ablation zone, which is continuously expanding due to enhanced glacier mass loss. The supraglacial debris transported over the melting glacier surface acts as an insulating barrier between the ice and atmospheric conditions and has a strong influence on the spatial distribution of surface ice melt. We conducted in-situ field measurements of point-wise ablation rate, supraglacial debris thickness, and debris temperature to examine the thermal resistivity of the debris pack and its influence on ablation over three glaciers (Bara Shigri, Batal, and Kunzam) in Chandra Basin of Western Himalaya during 2016–2017. Satellite-based supraglacial debris cover assessment shows an overall debris covered area of 15% for Chandra basin. The field data revealed that the debris thickness varied between 0.5 and 326 cm, following a spatially distributed pattern in the Chandra basin. The studied glaciers have up to 90% debris cover within the ablation area, and together represent ∼33.5% of the total debris-covered area in the basin. The supraglacial debris surface temperature and near-surface air temperature shows a significant correlation (r = &gt; 0.88, p = &lt; 0.05), which reflects the effective control of energy balance over the debris surface. The thermal resistivity measurements revealed low resistance (0.009 ± 0.01 m2°C W−1) under thin debris pack and high resistance (0.55 ± 0.09 m2°C W−1) under thick debris. Our study revealed that the increased thickness of supraglacial debris significantly retards the glacier ablation due to its high thermal resistivity.

Highlights

In the Hindu Kush Himalayan (HKH) region, about 13% of the glacierized area and ∼40% of the ablation area is debris-covered (Scherler et al, 2011; Bolch et al, 2012), which is expanding annually due to accelerated glacier mass loss (Shukla and Qadir, 2016)
The semi-automated analysis of Landsat 8 data showed that a significant area (∼15% of glacier area) of the 129 glaciers from Chandra basin is debris-covered
The field observations over the major glaciers of the Chandra basin showed that the lower ablation zone and area near to lateral moraines of these glaciers are covered by thick debris (∼100 cm)

Summary

Introduction

In the Hindu Kush Himalayan (HKH) region, about 13% of the glacierized area and ∼40% of the ablation area is debris-covered (Scherler et al, 2011; Bolch et al, 2012), which is expanding annually due to accelerated glacier mass loss (Shukla and Qadir, 2016). Debris cover accelerates water ponding and ice cliff (thermokarst erosion) formation over the glacier surface (Röhl, 2008) and can enhance heat transfer at the water-ice interface. Thermal resistance is an important index to understand the evolution of several glaciers (Nakawo and Young, 1982; Suzuki et al, 2007; Lambrecht et al, 2011; Chand and Sharma, 2015). This index is obtained from surface temperature and heat balance within the debris layers. Since it is difficult to determine the thermal resistance of a layer of unknown material directly in the field, it was suggested that the surface temperature of the debris layer may be used for estimating the thermal resistance (Suzuki et al, 2007)

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