Shifted sediment-transport regimes by climate change and amplified hydrological variability in cryosphere-fed rivers

Abstract

Climate change affects cryosphere-fed rivers and alters seasonal sediment dynamics, affecting cyclical fluvial material supply and year-round water-food-energy provisions to downstream communities. Here, we demonstrate seasonal sediment-transport regime shifts from the 1960s to 2000s in four cryosphere-fed rivers characterized by glacial, nival, pluvial, and mixed regimes, respectively. Spring sees a shift toward pluvial-dominated sediment transport due to less snowmelt and more erosive rainfall. Summer is characterized by intensified glacier meltwater pulses and pluvial events that exceptionally increase sediment fluxes. Our study highlights that the increases in hydroclimatic extremes and cryosphere degradation lead to amplified variability in fluvial fluxes and higher summer sediment peaks, which can threaten downstream river infrastructure safety and ecosystems and worsen glacial/pluvial floods. We further offer a monthly-scale sediment-availability-transport model that can reproduce such regime shifts and thus help facilitate sustainable reservoir operation and river management in wider cryospheric regions under future climate and hydrological change.

Seasonal dynamics of water and sediment in the permafrost basin of the Qinghai‐Tibet plateau and its driving factors

“…From May to October, the relationship between Q and SSC shows a clockwise variation (Figure 9a), with both variables increasing from spring, peaking in summer, and then declining. This pattern is consistent with findings from studies in other regions of the QTP plateau (Li, Overeem, et al, 2021; Zhang et al, 2023). However, at different event scales, when water–sediment variations are driven by individual events or several events simultaneously, there are differences in the SSC‐ Q variation curves.…”

“…Consequently, autumn exhibits high Q but low SSC, resulting in a smaller increase in SSF compared with spring (Figures 9a and 3). Zhang found that an increase in summer rainstorm events leads to amplified variability in river Q and higher peaks in SSC during the summer season (Zhang et al, 2023). The occurrence of summer rainstorm events results in an inverted ‘V’‐shaped variation in both Q and SSC (Figure 5), leading to an overall increase in sediment concentration and discharge fluctuations.…”

“…The snowmelt runoff dominated by temperature and the thawing of permafrost enhance soil erosion in the basin. The freeze–thaw cycles of permafrost contribute to the pronounced seasonality of water and sediment in these region (Li, Overeem, et al, 2021; Zhang et al, 2021; Zhang et al, 2023). Furthermore, the temperature‐driven retreat of glaciers in permafrost regions globally is exacerbating baisn soil erosion (Zhang et al, 2022).…”

“…Influenced by climate change, the melting of glaciers, thawing of snow cover, and permafrost contribute to the rise in runoff and sediment levels (Zhang et al, 2021). The intensification of extreme rainfall events and the increased meltwater from glaciers are exacerbating erosion on slopes and river channels (Zhang et al, 2023). Existing studies have not only concluded that sediment transport continues to increase, but have also identified differences in different seasons and their driving factors, such as the dominance of snow and permafrost thawing in spring and rainfall in summer (Li et al, 2023; Li, Lu, et al, 2021).…”

“…Through our seasonal-scale study, we have found that temperature is the primary factor driving runoff and sediment production in both spring and autumn, whereas rainfall is the main factor in summer (Figure 7). Studies in the northern QTP and the Tianshan region have shown that the decreasing snowmelt in spring and increasing rainfall events are gradually shifting the drivers of runoff and sediment production from temperature-driven to rainfall-driven in spring (Zhang et al, 2023). The latest research indicates that under the continuous degradation of the cryosphere, future runoff and sediment production in the basin will be controlled by rainfall (Zhang et al, 2022).…”