Improving the Representation of Polar Snow and Firn in the Community Earth System Model Journal of Advances in Modeling Earth Systems

In Earth system models, terrestrial snow is usually modeled by the land surface component. In most cases, these snow models have been developed with an emphasis on seasonal snow. Questions about future sea level rise, however, prompt the need for a realistic representation of perennial snow, as snow pro-cesses play a key role in the mass balance of glaciers and ice sheets. Here we enhance realism of modeled polar snow in the Community Land Model (CLM), the land component of the Community Earth System Model (CESM), by implementing (1) new parametrizations for fresh snow density, destructive metamor-phism, and compaction by overburden pressure, (2) by allowing for deeper snow packs, and (3) by introduc- ing drifting snow compaction, with a focus on the ice sheet interior. Comparison with Greenlandic and Antarctic snow density observations show that the new physics improve model skill in predicting firn andnear-surface density in the absence of melt. Moreover, compensating biases are removed and spurious sub-