Debris flows originating in the mountain cryosphere under a changing climate: A review

Abstract

Debris flows originating in the mountain cryosphere (DFMC) are one of the most globally important, widely distributed mass flows (and natural geohazards) in mountain areas with a high altitude and/or high latitude. This is particularly the case in high mountain areas that have been undergoing rapid glacier retreat, permafrost degradation, and other melt/thaw related processes. As a consequence, the actual hazards and potential risks of DFMC have drawn increasing attention in the context of global climate change (i.e. a rising temperature and higher occurrence of strong precipitation events). Unlike debris flows at low elevations, where their occurrence is closely related to precipitation (intensity and duration), the breach of a DFMC event depends on precipitation and/or air temperature, which in turn influence melt/thaw processes, rending the formation mechanism much more complicated. Although research has been widely carried out on DFMC in past decades, there is still a long way to go before we have reached a complete understanding of the formation mechanism and triggering conditions. This review summarizes recent progress in the study of DFMC, including typical DFMC events and their causes, the failure mechanisms of rock (or ice-rock joints), the characteristics of moraine deposits, initiation through hydraulic erosion (entrainment), the relationship between DFMC initiation and meteorological conditions, and the slope stability of the mountain cryosphere under a changing climate. Several issues that should be addressed in future research are also discussed.