Explore the world's cold regions

Over the past decades, the world’s cryospheric regions, ranging from mountain headwaters to polar coastal areas, have experienced unprecedented atmospheric warming, glacier melting, and permafrost thaw. Although the associated hydrological-geomorphic changes have been widely documented, the associated increases in erosion and sediment fluxes have yet been fully recognized by the scientific society and local decision-makers.

Ongoing cryosphere degradation has expanded the extent of unstable landscapes and enhanced sediment mobilization by forming glacier debuttressing valleys, accessing sub-/pro-glacially stored sediment, and creating thermokarst hillslopes. With continuous cryosphere degradation, sediment transport will increase until reaching a maximum (Peak Sediment). Thereafter, transport will likely shift from a temperature-dominated regime toward a rainfall-dominated regime roughly between 2100-2200. Changes in sediment fluxes and regimes have wide-reaching social-ecological consequences by impairing water quality, hampering hydropower infrastructure, and threatening water-food-energy security for nearly 2 billion people living in or downstream of mountain areas.

In this review, we summarize the magnitudes of ongoing cryosphere degradation; detail the mechanisms of erosion and sediment transport in cold regions; conceptualize the likely future trends of sediment yields; discuss the related challenges and uncertainties. Based on over 80 publications, we identify a 2-8 fold increase in sediment fluxes and more than doubled coastal erosion rates in many cold regions between the 1950s and 2010s. Moreover, we offer a global inventory of cryosphere degradation-driven increases in erosion and sediment yield, with 76 locations from the high Arctic, European mountains, High Mountain Asia and Andes, and 18 Arctic permafrost-coastal sites.

By reflecting changes in meltwater and erodible landscapes ( Li et. al., 2021 ), theoretical sediment transport regimes may shift through three temporal stages separated by the timing of peak meltwater and completion of deglaciation, regardless of glacier re-advancing, (dis-)connectivity changes, scale/threshold effects in sediment transport, the stabilization rate of deglaciated landscapes, and human interference.

• Zhang, T., Li, D., & Lu, X. (2022).  Response of runoff components to climate change in the source-region of the Yellow River on the Tibetan plateau . Hydrological Processes, 36( 6).
• Li, D., Lu, X., Walling, D.E. et al.  High Mountain Asia hydropower systems threatened by climate-driven landscape instability . Nat. Geosci. 15, 520–530 (2022).
• Zhang, T., Li, D., Kettner, A. J., Zhou, Y., & Lu, X. (2021).  Constraining dynamic sediment-discharge relationships in cold environments: The sediment-availability-transport (SAT) model.  Water Resources Research, 57, e2021WR030690.
• Li, D., Lu, X., Overeem, I., Walling, D. E., Syvitski, J., Kettner, A. J., ... & Zhang, T. (2021).  Exceptional increases in fluvial sediment fluxes in a warmer and wetter High Mountain Asia . Science, 374(6567), 599-603.
• Li, D., Overeem, I., Kettner, A. J., Zhou, Y., & Lu, X. (2021).  Air temperature regulates erodible landscape, water, and sediment fluxes in the permafrost-dominated catchment on the Tibetan Plateau.  Water Resources Research, 57, e2020WR028193.
• Li, D., Li, Z., Zhou, Y., & Lu, X. (2020).  Substantial increases in the water and sediment fluxes in the headwater region of the Tibetan Plateau in response to global warming.  Geophysical Research Letters, 47, e2020GL087745.
• Li, D., Lu, X. X., Chen, L., and Wasson, R. J. (2019)  Downstream geomorphic impact of the Three Gorges Dam: With special reference to the channel bars in the Middle Yangtze River.  Earth Surf. Process. Landforms, 44: 2660– 2670.
• Li, D., Lu, X. X., Yang, X., Chen, L., & Lin, L. (2018).  Sediment load responses to climate variation and cascade reservoirs in the Yangtze River: A case study of the Jinsha River.  Geomorphology, 322, 41-52.

zhang_ting@u.nus.edu

dongfeng@u.nus.edu