Patterns and drivers of glacier debris-cover development in the Afghanistan Hindu Kush Himalaya

Debris-covered ice is widespread in mountain regions with debris an important control on surface ice melt and glacier retreat. Quantifying debris cover extent and its evolution through time over large regions remains a challenge. This study develops two Normalized Difference Supraglacial Debris Indices for mapping debris-covered ice based on thermal and near Infrared Landsat 8 bands. They were calibrated with field data. Validation suggests that they have a high level of accuracy. They are then applied to Landsat data for 2016 to produce the first detailed glacier inventory of the Afghanistan Hindu Kush Himalaya that includes debris cover. 3408 glaciers were identified which, for those > 0.01 km(2) in area, gives an ice cover of 2,222 +/- 11 km(2) and a debris cover of 619 +/- 40 km(2). Principal components analysis was used to identify the most influential drivers of debris-covered ice extent. Lower proportions of debris cover were associated with glaciers with a higher elevation range, that were larger, longer and wider. These relations were statistically clearer when the dataset was broken down into climate and geological zones. A glaciers continue to shrink, the proportion of debris cover will become higher, making it more important to map debris cover reliably.

Automated summary

This study develops two Normalized Difference Supraglacial Debris Indices for mapping debris-covered ice based on thermal and near Infrared Landsat 8 bands. They were calibrated with field data and validated to have high accuracy. The indices were then applied to Landsat data for 2016 to produce a detailed glacier inventory of the Afghanistan Hindu Kush Himalaya that includes debris cover. Principal components analysis identified the main drivers of debris-covered ice extent, and it was found that as glaciers shrink, the proportion of debris cover will become higher, emphasizing the importance of reliable debris cover mapping.