Global debris thickness estimates of debris-covered glaciers

Debris-covered glaciers are common in many parts of the world including Alaska, Europe, High Mountain Asia, and New Zealand. The thickness of this debris and its spatial distribution is critical to the evolution of debris-covered glaciers as a thin layer may enhance surface melt, while a thick layer may reduce it. Despite debris covering ~4% of the global glacier area (excluding the ice sheets) and upwards of 23% in various regions, few debris-covered glaciers have in-situ measurements of the debris thickness. This provides a major obstacle for glacier evolution models to account for debris-covered glaciers. Here we present the first globally distributed estimates of debris thickness using a novel method that utilizes computational models and remote sensing data. Our debris thickness estimates agree well with in-situ measurements. The spatial distribution of debris thickness at the glacier scale shows debris is thicker near the glacier termini and thinner further upglacier. These debris thickness estimates are used to quantify how accounting for debris cover affects sub-debris glacier melt at the glacier, regional, and global scale. We find that accounting for debris can substantially impact regional glacier mass balance.