Method dependence in thermal conductivity and aerodynamic roughness length estimates on a debris‐covered glacier

Rock debris partially covers glaciers worldwide, with varying extents and distributions, and controls sub‐debris melt rates by modifying energy transfer from the atmosphere to the ice. Two key physical properties controlling this energy exchange are thermal conductivity (k) and aerodynamic roughness length (z0). Accurate representation of these properties in energy‐balance models is critical for understanding climate‐glacier interactions and predicting the behavior of debris‐covered glaciers. However, k and z0 have been derived at very few sites from limited local measurements, using different approaches, and most model applications rely on values reported from these few sites and studies. We derive k and z0 using established and modified approaches from data at three locations on Pirámide Glacier in the central Chilean Andes. By comparing methods and evaluating melt simulated with an energy‐balance model, we reveal substantial differences between approaches. These lead to discrepancies between ice melt from energy‐balance simulations and observed data, and highlight the impact of method choice on calculated ice melt. Optimizing k against measured melt appears a viable approach to constrain melt simulations. Determining z0 seems less critical, as it has a smaller impact on total melt. Profile aerodynamic method measurements for estimating z0, despite higher costs, are independent of ice melt calculations. The large, unexpected differences between methods indicate a substantial knowledge gap. The fact that field‐derived k and z0 fail to work well in energy‐balance models, suggests that model values represent bulk properties distinct from theoretical field measurements. Addressing this gap is essential for improving glacier melt predictions.