Model Output

The model outputs a variety of data including monthly mass balance and its components (accumulation, melt, refreezing, frontal ablation, glacier runoff), and annual mass, mass below sea level, and area. Results are written as a netcdf file (.nc) for each glacier. If multiple simulations are performed (e.g., for Monte Carlo simulations), then statistics related to the median and median absolute deviation are output for each parameter.

In addition to this standard glacier-wide output, binned outputs are also available (by setting sim["out"]["export_binned_data"] to true in the PyGEM configuration file), which include each bins initial surface elevation, annual area, annual mass, annual thickness, annual climatic mass balance, and monthly climatic mass balance. Monthly climatic mass balance components can also be stored by setting sim["out"]["export_binned_components"] to true.

Post-processing Data

PyGEM simulations are output for each glacier individually. For most analyses, it is useful to aggregate or merge analyses to a regional or global scale. PyGEM’s postproc.compile_simulations.py is designed to do just so.

This script is designed to aggregate by region, scenario, and variable. For example the following call will result in 8 output files, the annual glacier mass and the annual glacier area for each specified scenario, for each specified region

compile_simulations -rgi_region 01 02 -scenario ssp245 ssp585 -gcm_startyear2000 -gcm_endyear 2100 -vars glac_mass_annual glac_area_annual

See below for more information.

Analyzing Results

Various Jupyter Notebooks are provided for analyzing PyGEM results in a separate GitHub repository.

• analyze_regional_change.ipynb.ipynb
  This notebook demonstrates how to aggregate simulations by region and plot the glacier mass, area, and runoff changes.

• analyze_glacier_change_byWatershed.ipynb
  This notebook can be used to aggregate glacier mass, area, and runoff into watersheds; specifically, it will create new netcdf files per watershed such that after the initial aggregation, analyses can be performed much more rapidly. The notebook continues to show an example plot of glacier mass, area, and runoff changes for each watershed in an example region:

Note

This notebook assumes that you have a “dictionary”, i.e., a .csv file, that has each glacier of interest and the watershed (or other grouping) name associated with each glacier.

• analyze_glacier_change_CrossSection.ipynb
  This notebook can be used to plot cross sections of an individual glacier’s ice thickness over time for an ensemble of GCMs: