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Abstract Most of the central Himalayan glaciers have surface debris layers of variable thickness, which greatly affect the ablation rate. An attempt has been made to relate debris-cover thickness to glacier surface melting. Thirty stakes were used to calculate ablation for debris-covered and clean ice of Dokriani Glacier (7 km 2 ) from 2009/10 to 2012/13. Our study revealed significant altitude-wise difference in the rate of clean and debris-covered ice melting. We found a high correlation ( R 2 = 0.92) between mean annual clean-ice ablation and altitude, and a very low correlation ( R 2 = 0.14) between debris-covered ice melting and altitude. Debris-covered ice ablation varies with variation in debris thickness from 1 to 40 cm; ablation was maximum under debris thicknesses of 1–6 cm and minimum under 40 cm. Even a small debris-cover thickness (1–2 cm) reduces ice melting as compared to that of clean ice on an annual basis. Overall, debris-covered ice ablation during the study period was observed to be 37% less than clean-ice ablation. Strong downwasting was also observed in the Dokriani Glacier ablation area, with average annual ablation of 1.82 m w.e. a –1 in a similar period. Our study suggests that a thinning glacier rapidly becomes debris-covered over the ablation area, reducing the rate of ice loss.
Pratap et al. (2014) studied this question.