Inventory and , motion changes of and acceleration of rock glacier creep speeds s in Ile Alatau and Kungöy Ala-Too, northern Tien Shan, since the 1950s

Spatio-temporal patterns of rock glacier creeprelated to the viscous creep in perennially frozen sediments of rock glaciers in cold mountains have rarely been studied outside the densely populated European Alps. This study investigates the spatial and temporal variability of rock glacier movementtion in the Ile Alatau and Kungöy Ala-Too mountain ranges, northern Tien Shan, a region with particularly large and fast rock glaciers. Over the study region of more than 3000 km, an inventory 20 of slope movements is constructed using a large number of radar interferograms and high-resolution optical imagery. The inventory includes more than 900 landforms, of which around 550 are interpreted as rock glaciers. Out of the active rock glaciers inventoried, 45 are characterised by a rate of motion exceeding 100 cm/a. From these fast rock glaciers we select six (Gorodetzky, Morenny, Archaly, Ordzhonikidze, Karakoram and Kugalan Tash) and study them in more detail (Gorodetzky, Morenny, Archaly, Ordzhonikidze, Karakoram and Kugalan Tash rock glaciers) using offset tracking between repeat airphotos, 25 and historical and modern very high resolution optical satellite data. Most Two of these rock glaciersm show an overalla steady increase of decadal surface velocities from the 1950s onwards with speeds being roughly two to three four times higher in recent years compared to the 1950s and 1960s. Three rock glaciers show similar accelerations over the recent one to two decades, but also phases of increased speeds in the 1960s. This development indicates a possible significant increase in current sediment and ice fluxes through rock glaciers and implies that – when compared to glacier shrinkage – periglacialtheir material 30 sediment transport in the region seems tomight gain geomorphodynamic importance relative to glacial material sediment transport by glaciers, assuming the latter decreases together with the regional glacier shrinkage. The study demonstrates how air and satellite image archives are exploited to construct one of the longest decennial times series of rock glacier speeds