Stream hydrology controls on ice cliff generation, evolution, and survival on debris-covered glaciers

Abstract. Ice cliffs are melt hot spots that contribute disproportionately to melt on debris-covered glaciers. In this study, we investigate the impact of supraglacial stream hydrology on ice cliffs using in-situ and remote sensing observations, stream flow measurements, and a conceptual geomorphic model of ice cliff backwasting applied to ice cliffs on Kennicott Glacier, Alaska. We found that 31.4 % of ice cliffs are actively influenced by streams, while 46.4 % are less than 10 m from the nearest stream. Supraglacial streams contribute to ice cliff formation and maintenance by horizontal meandering, vertical incision, and debris transport. Meander morphology reminiscent of sedimentary river channel meanders and oxbow lakes leads to sinuous or crescent-shaped ice cliff shapes. Stream action at the base of ice cliffs aids in cliff maintenance by enhancing incision and preventing reburial. These processes produce an undercut lip and transport clasts up to tens of centimeters in diameter. Stream avulsions result in rapid ice cliff collapse and local channel abandonment. Ice cliffs abandoned by streams are observed to be reburied by supraglacial debris, indicating a strong role played by streams in ice cliff persistence. The development of landscape evolution models may assist in quantifying the total net effect of these processes on steady state ice cliff coverage and mass balance on debris-covered glaciers.