A framework for characterizing fluvial sediment fluxes from source to sink in cold environments. Geogr. Ann. 92 A (2): 155-176. to better assess the sensitivity of cold environments to environmental change within the context of contemporary and past sediment flux.

Rapid atmospheric warming since the mid-20th century has increased temperature-dependent erosion and sediment transport processes in cold environments, impacting food, energy and water security. In this Review, we summarize landscape changes in cold environments and provide a global inventory of cryosphere degradation-driven increases in erosion and sediment yield. Anthropogenic climate change, deglaciation, and thermokarst disturbances are causing increased sediment mobilization and transport processes in glacierized and peri-glacierized basins. With continuous cryosphere degradation, sediment transport will continue to increase until reaching a maximum (peak sediment). Thereafter, transport will likely shift from a temperaturedependent regime toward a rainfall-dependent regime roughly between 2100-2200. The timing of the regime shift would be regulated by changes in meltwater, erosive rainfall and landscape erodibility, and complicated by geomorphic feedbacks and connectivity. Further progress in integrating multi-source sediment observations, developing physics-based sediment transport models, and enhancing interdisciplinary and international scientific collaboration are needed to predict sediment dynamics in a warming world. Key points1. A global inventory of cryosphere degradation-driven increases in erosion and sediment yield is presented, with 76 locations from the high Arctic, European mountains, High Mountain Asia and Andes, and 18 Arctic permafrost-coastal sites.2. Sediment mobilization from glacierized basins is dominated by glacial and paraglacial erosion; transport efficiency is controlled by glacio-hydrology and modulated by sub-, pro-, supra-glacial storage and release but is interrupted by glacial lakes and moraines.3. Degraded permafrost mainly mobilizes sediment by eroding thermokarst landscapes in high-latitude terrain and unstable rocky slopes in high-altitude terrain, which is sustained by exposing and melting ground ice and sufficient water supply; transport efficiency is enhanced by hillslope-channel connectivity.4. The sediment transport regime will shift in three stages, from a thermal-controlled regime to one jointly control by thermal and pluvial processes, and finally to a regime controlled by pluvial processes. 5. Peak sediment yield will be reached with or after peak meltwater.2 / 37 6. Between the 1950s and 2010s, sediment fluxes have increased by 2-8 folds in many cold regions and coastal erosion rates have more than doubled along many parts of Arctic permafrost coastlines.

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In the Latnjavagge drainage basin (68°21′N, 18°29′E), an arctic‐oceanic periglacial environment in northernmost Swedish Lapland, the fluvial sediment transport and the characteristics and importance of high‐magnitude/low‐frequency fluvial events generated by intense snowmelt or heavy rainfall have been investigated and compared with snowmelt‐ and rainfall‐induced discharge peaks in the Levinson‐Lessing Lake basin (Krasnaya river system) on the Taimyr Peninsula, an arctic periglacial environment in northern Siberia (74°32′N, 98°35′E). In Latnjavagge (9 km2) the intensity of fluvial sediment transport is very low. Most of the total annual sediment load is transported in a few days during snowmelt generated runoff peaks. Due to the continuous and very stable vegetation covering most areas below 1300 m a.s.l. in the Latnjavagge catchment, larger rainfall events are of limited importance for sediment transport in this environment. Compared to that, in the c. 40 times larger Krasnaya riversystem rainfall‐generated runoff peaks cause significant sediment transport. The main sediment sources in the Latnjavagge drainage basin are permanent ice patches, channel debris pavements mobilized during peak discharges and exposing fines, and material mobilized by slush‐flows. In the Krasnaya river system river bank erosion is the main sediment source. In both periglacial environments more than 90% of the annual sediment yield is transported during runoff peaks. The results from both arctic periglacial environments underline the high importance of high‐magnitude/low‐frequency fluvial events for the total fluvial sediment budgets of periglacial fluvial systems. Restricted sediment availability is in both arctic environments the major controlling factor for this behaviour.