The state of rock debris covering Earth’s glaciers

• Published in: Nature Geoscience
• Main Authors: Herreid, Samuel, Pellicciotti, Francesca
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Publishing 2020
• Subjects: F600 Geology; F800 Physical and Terrestrial Geographical and Environmental Sciences; Greenland; glacier; glaciers; Alaska
• Online Access: https://nrl.northumbria.ac.uk/id/eprint/44493/; https://doi.org/10.1038/s41561-020-0615-0; https://nrl.northumbria.ac.uk/id/eprint/44493/1/Pellicciotti_2020a.pdf

Rock debris can accumulate on glacier surfaces and dramatically reduce glacier melt. The structure of a debris cover is unique to each glacier and sensitive to climate. Despite this, debris cover has been omitted from global glacier models and forecasts of their response to a changing climate. Fundamental to resolving these omissions is a global map of debris cover and an estimate of its future spatial evolution. Here we use Landsat imagery and a detailed correction to the Randolph Glacier Inventory to show that 7.3% of mountain glacier area is debris covered and over half of Earth’s debris is concentrated in three regions: Alaska (38.6% of total debris-covered area), Southwest Asia (12.6%) and Greenland (12.0%). We use a set of new metrics, which include stage, the current position of a glacier on its trajectory towards reaching its spatial carrying capacity of debris cover, to quantify the state of glaciers. Debris cover is present on 44% of Earth’s glaciers and prominent (>1.0 km2) on 15%. Of Earth’s glaciers, 20% have a substantial percentage of debris cover for which the net stage is 36% and the bulk of individual glaciers have evolved beyond an optimal moraine configuration favourable for debris-cover expansion. Use of this dataset in global-scale models will enable improved estimates of melt over 10.6% of the global glacier domain.