Steep ice – progress and future challenges in research on ice cliffs

Ice cliffs are features along ice sheet margins, along tropical mountain glaciers, at termini of mountain glaciers and on debris-covered glacier tongues, that have received scattered attention in literature. They cover small relative areas of glacier or margin surface respectively, but have been involved in two apparent anomalies. On the one hand, they have been identified as potential hotspots of extreme melt rates on debris-covered tongues contributing to their relatively rapid ablation, compared to the surrounding glacier surface. On the other hand, they appear where the ice margin is stable (or temporarily advancing) even under conditions of negative mass balance. In this manuscript, we recapitulate why ice cliffs remain interesting features to investigate and what we know about them so far. We conclude by suggesting to further investigate their genesis and variable morphology and their potential as windows into past climates and processes.