Abstract
Debris covers glaciers worldwide and controls sub-debris melt rates by
modifying energy transfer from the atmosphere to the ice. Physical
properties like thermal conductivity (k) and surface roughness
(z0) have been derived from limited local measurements, with
models often relying on literature values from a few sites and studies.
Accurate representation of these properties in energy-balance models is
crucial for understanding climate-glacier interactions and predicting
future behaviour of debris-covered glaciers. We studied these properties
using established and modified approaches to derive k and z0
from field data at three locations on Pirámide Glacier in the central
Chilean Andes. We compared existing methods and evaluated the modelled
melt using these values. Our study reveals substantial inconsistencies
between methods, leading to discrepancies between ice melt from
energy-balance simulations and observed data, highlighting the impact of
method choice on calculated ice melt. For energy-balance modelling,
optimising k against measured ice melt appears a viable method to
constrain melt simulations. Determining z0 is less critical due to
its smaller impact on total ice melt, and profile aerodynamic method
measurements, despite higher economic costs, are independent of ice melt
calculations. The large, unexpected differences between existing methods
indicate a substantial knowledge gap that the community should address.
Values of k and z0 from field measurements do not work well
when used in energy-balance models, suggesting that model values are
bulk properties that do not necessarily correspond to field-derived
values from theoretical approaches.