Coupling a Global Glacier Model and Hydrological Model: Constraining Cryospheric Contributions in the Data-Scarce Indus Basin

Climate warming is rapidly modifying glacier and snowmelt processes, with impacts that propagate across spatial and temporal scales, from high-elevation cryospheric dynamics to basin-scale streamflow. Capturing these cross-scale interactions requires hydrological models that explicitly represent cryospheric processes, such as glacier dynamics and snow redistribution, while also accounting for uncertainty arising from data scarcity and model structure. To address these challenges, we present a one-way coupling that integrates the Global Glacier Evolution Model (GloGEM) with Raven, a flexible hydrological modeling framework designed to emulate multiple model structures for systematic uncertainty assessment. Glacier simulations are first improved by incorporating snowline observations as an additional calibration constraint to the geodetic mass balance, reducing parameter equifinality and enhancing glacier runoff estimates. The resulting glacier runoff is then provided to the hydrological model, leading to a more robust representation of snowmelt processes and their contribution to streamflow. By evaluating multiple hydrological model structures within Raven, we further quantify uncertainties in simulated melt contributions arising from structural model choices. The framework is applied to multiple data-scarce Indus headwaters as representative high-mountain catchments, simulating melt contributions and streamflow across scales. By explicitly coupling cryosphere and hydrological models, this framework aims to improve projections of future water availability in data-scarce regions and provides a transferable approach for integrated cryosphere-hydrology modeling in complex mountain regions.