Warming-driven erosion and sediment transport in the world’s cold regions
Journal Article
Overview
abstract
The world’s cryospheric regions, ranging from high mountains to polar regions, have experienced unprecedented atmospheric warming, glacier melting and permafrost thawing since the mid-20th century. This rapid cryosphere degradation has dramatically altered terrestrial/coastal landscapes, characterized by creating debuttressed valleys and thermokarst hillslopes, expanding unstable landscapes, and increasing the access to sub-/pro-glacially stored sediment. Such rapid landscape changes have resulted in increases in erosion and sediment loads, posing threats to riverine and near-shore marine environments and triggering cascading impacts on water-food-energy securities which support the livelihoods of a quarter of the global population.Here, we present a global inventory of cryosphere degradation-driven increases in erosion and sediment yield, including 76 locations from the high Arctic, European mountains, High Mountain Asia and Andes, and 18 Arctic permafrost-coastal sites, collected from over 80 publications. This inventory confirms the widespread increase in sediment transport from cold regions in response to modern deglaciation. Moreover, we identify two to eight-fold increases in sediment fluxes and more than doubled coastal erosion rates in many cold regions between the 1950s and 2010s.Such increases in sediment evacuation from deglaciating/thermokarst regions have been blamed for introducing large amounts of carbon, nitrogen, and pollutants into aquatic ecosystems, impacting primary productivity, river biodiversity, and water quality. In high-mountain areas, increased sediment fluxes have also hampered hydropower exploitation through reservoir sedimentation and turbine abrasion. Meanwhile, accelerated erosion along ice-rich Arctic permafrost coasts has caused an irreversible land loss, costing billions of dollars for relocating or protecting coastal infrastructure.With continuous cryosphere degradation, sediment fluxes are likely to increase in the next decades until reaching a maximum (“Peak Sediment”). Theoretically, the timing of peak sediment can lag decades to hundreds of years behind the peak meltwater due to the remobilization of paraglacial and subglacial sediment legacy. Thereafter, sediment fluxes will decline as glacier/permafrost erosion ceases and active sediment contributing area shrinks. We predict that sediment-transport regimes will shift through three stages, from the ongoing temperature-dominated regime to a temperature-precipitation jointly controlled regime, eventually shifting toward a rainfall-dominated regime roughly between 2100-2200.However, the understanding of sediment dynamics in cold regions is still limited by the lack of long-term observations and the inherent complexity of geomorphic processes, such as episodic events, scale/threshold effects in sediment transport, and positive/negative feedbacks of geomorphic responses. To underpin the forward-looking mitigation strategies for climate-sensitive and fragile cold regions, we call for the enhancement of multi-source sediment monitoring programs, fully distributed physics-based sediment-yield models, and interdisciplinary-international scientific collaborations.
