Are rock glaciers useful climate indicators?

Abstract Rock glaciers are ice-bearing, creeping landforms of the cryosphere, and their spatial occurrence and deformation velocity are sensitive to climate. Permafrost research has made several attempts to use this climate sensitivity to establish rock glaciers as climate indicators. A recent initiative succeeded to make rock glacier velocity (RGV) a quantity of the essential climate variable (ECV) permafrost. To justify this step, the initiators formulated the role of rock glaciers for the ECV permafrost with caution. In scientific practice, however, reference was made to the initiative in order to interpret the relevance of RGV more broadly and attribute a direct role of a climate indicator to it. This ambivalence should be converted into a consensus, recognizing the need for long-term rock glacier monitoring, but at the same time agreeing on the limits of a reasonable interpretation of RGV. Rock glacier-based paleoclimatology constitutes a second important approach to use rock glaciers as climate proxies. It is based on the comparison of the spatial distribution of active and relict rock glaciers to derive a climate signal. With slightly varying methodology, this approach has been used in numerous publications and over several decades. Taken together, the results reveal considerable variations, some of which are a consequence of conceptual weaknesses. Considering the current state of knowledge on rock glacier formation and referring to alternative climate reconstructions, the possibilities and limits of rock glacier-based paleoclimatology are evaluated. This review evaluates the general suitability of rock glaciers as climate indicators, particularly in comparison to other climate indicators from the research field of mountain permafrost. At the same time, it emphasises their complex climate sensitivity and the resulting need to monitor and investigate rock glaciers, since they play a significant role in alpine mass wasting and can be a hazard potential for mountain communities.