Glacier Energy and Mass Balance (GEMB): a model of firn processes forcryosphere research

This paper provides the first description of theopen-source Glacier Energy and Mass Balance model. GEMB models the ice sheetand glacier surface-atmospheric energy and mass exchange, as well as the firn state. Itis a column model (no horizontal communication) of intermediate complexitythat includes those processes deemed most relevant to glacier studies. GEMBprioritizes computational efficiency to accommodate the very long (thousandsof years) spin-ups necessary for initializing deep firn columns andsensitivity experiments needed to characterize model uncertainty oncontinental scales. The model is one-way coupled with the atmosphere, whichallows the model to be run offline with a diversity of climate forcing butneglects feedback to the atmosphere. GEMB provides numerous parameterizationchoices for various key processes (e.g., albedo, subsurface shortwaveabsorption, and compaction), making it well suited for uncertaintyquantification and model exploration. The model is evaluated against thecurrent state of the art and in situ observations and is shown to performwell.