Climate-driven regime shifts and amplified seasonality in sediment transport of cryosphere-fed rivers

The unprecedented atmospheric warming, coupled with extensive cryosphere degradation, has triggered profound changes in terrestrial landscapes and hydrogeomorphic processes. Rapidly increasing temperature-dependent erosion in cryospheric regions is releasing vast quantities of unconsolidated sediment. Together with altered hydrological processes, shifts in the timing and magnitude of fluvial fluxes have been widely identified in cryosphere-featured rivers. Notably, the substantial increase in summer sediment transport can be attributed to rich sediment sources activated by thaw-related processes and greater glacier meltwater pulses and pluvial pulses. Such amplified seasonality in sediment transport has crucial implications as they fundamentally alter the seasonal allocation of organic matter, nutrients and pollutants, thus affecting the year-round provision of water, food, and energy to populated and vulnerable mountain communities. Continuous glacier retreat and permafrost degradation are expected to further elevate sediment fluxes in the coming decades until reaching the maximum (“peak sediment”). The timing of this peak may lag behind the meltwater peak by decades or even centuries, driven by the legacy effects of fluvial transport and the remobilization of sediment deposited in proglacial and periglacial regions. As thermally-controlled sediment sources are depleted, we predict that sediment-transport regimes will shift from the ongoing temperature-dominated regime toward a rainfall-dominated regime after the completion of deglaciation. Understanding regime shifts and associated tipping points in sediment transport is essential for safeguarding downstream riverine ecosystems and enabling adaptive, forward-looking basin management strategies.