Regional Mountain Conference

Glacier evolution modelling employs either temperature-index (TI) or energy-balance formulations. Temperature-index requires only air temperature to simulate melt. However, the parameters on which it depends (e.g. the Degree-Day factor) do not have any physical basis and arise simply from calibration – and are expected to vary on a glacier-by-glacier basis, forcing any projections made to rely on a curve-fitting exercise that may not apply in the future.

Energy-balance modelling takes account of transfer of heat through radiation and convection, and in general processes within the snowpack such as refreezing. The former is very computationally inexpensive and is used far more widely; while the latter is computationally more expensive and requires more atmospheric inputs (often at higher frequencies) but is more physically-based and more likely to apply to future scenarios.

This study integrates a energy-balance snow/glacier column model, factorial snowpack model (FSM), with a glacier evolution model, the Open Global Glacier Model (OGGM). Typically, OGGM uses temperature-index technique (i.e. TI-OGGM) while this study replaces it with FSM. Both are extremely computationally efficient. Additionally, FSM-OGGM generates output at daily scale (instead of monthly outputs of OGGM), which is beneficial to hydrological modelling.

Here we carry out a comparison between TI-OGGM and FSM-OGGM applied to the Rofental catchment, Austria. Climate data from the GSWP3-W5E5 are used as reference from 1980 to 2020; TI-OGGM is calibrated to the region while FSM-OGGM is not. Both models agree well with glacier-wide mass balance over this period, but both show large deviations from observations when mass-balance profiles are considered, and this has impact on modelled retreat. The results indicate shortcomings in the FSM-OGGM, but ones which can be addressed by improved calibration; this is a subject of ongoing effort.