Journal Article

Climate‐Driven Changes to Suspended‐Sediment Yields by the End of the Century

Pelletier, Jon D., Prescott, Alexander B.

2025

Overview

Anticipated changes in climate by the end of this century are likely to modify suspended‐sediment yields (Sy) in diverse ways. Past work has shown how hydrological non‐stationarity may alter water discharges and hence Sy, but less attention has been given to the impact of likely future changes in upland sediment‐detachment rates on downstream Sy. In certain environments, climatically driven changes in vegetation cover on upland hillslopes may more than counteract the effects of changing runoff on Sy. Changes in precipitation, temperature, and vegetation may, therefore, interact in nonlinear ways to produce unexpected changes. In this work, we simulated future changes to background Sy (i.e., changes unrelated to land‐use changes and dams) with climatological and vegetative data output from an ensemble of CMIP6 Earth System Model (ESM) simulations. Depending on the future scenario, the cumulative annual sediment flux of 780 globally distributed rivers increases by between 2.3% and 8.4%. Significant deviations from historical Sy are projected at high latitudes in response to each forcing variable, while low‐latitude responses are regionally varied. In regions where ensemble members agree on future changes in forcing variables, large Sy changes are forecast with high confidence (e.g., >200% Sy increase for several northeastern U.S. rivers at the 95% level). In contrast, ensemble variability in vegetation projections results in considerable uncertainty in the projected Sy of rivers in other regions. Further improvements to the vegetation components of ESMs will help to reduce regional uncertainties in projected changes to Sy. Plain Language Summary Rivers move sediment eroded from across the landscape downstream through mountains, valleys, and deltas, carrying small‐enough grains in suspension over long distances from source to sink. The amount of suspended sediment a river transports varies according to flow competence and upstream basin characteristics, but anthropogenic climate change could alter baseline sediment mobilization rates in complex ways that cascade through river networks and disturb both natural and human systems. In this study, we combined a multi‐scenario ensemble of earth system models with a global suspended‐sediment‐flux model calibrated to natural conditions in order to understand how future changes in temperature, precipitation, and vegetation will translate into adjustments to the sediment delivered to large river deltas. We find that across future scenarios, cumulative sediment transport will increase by 2%–8% by the year 2100, but many regions (especially at high latitudes) may see declines locally due to greater vegetative cover that reduces the erosive potential of rainfall. Altogether, our results indicate that rivers in the near future may experience large changes in sediment loading, and improvements to dynamic vegetation models will improve confidence in projections of suspended‐sediment fluxes. Key Points We provide spatially distributed ensemble projections of global suspended‐sediment‐yield responses to anthropogenic climatic changes by 2100 We project a median increase of 2.3%–8.4% in the cumulative suspended‐sediment flux of 780 globally distributed rivers Shifts in vegetation, temperature, and rainfall drive significant regional and latitudinal changes in hillslope sediment‐detachment rates

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Bayesian inference / Climate change / Datasets / ensemble projections / Floodplains / Floods / global climate change / Land use / Latitude / Precipitation / Rain / Rivers / Runoff / sediment detachment / sediment transport / Sediment yield / Sediment, Suspended / Sediments / Soil erosion / Suspended sediment / suspended sediment yield / Topography / Uncertainty / Variables / Vegetation / Vegetation cover / Water discharge