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Spectral snow albedo in a regional climate model: application to the Greenland and Antarctic ice sheets

An important part of the climate system of Earth are the ice sheets of Greenland and Antarctica. Crucial for the development of an ice sheet is the reflectivity of sunlight, or albedo, at the surface. To better understand a process like albedo and the climate system of the past, present and future, we use regional climate models. There is still room for improvements in such models, however, as the description of some processes like snow albedo is rather limited. The goal of this research is therefore to implement a new snow albedo scheme in the climate model RACMO2, and analyze its impact on the development of the major ice sheets. In this study, we present the steps taken, discuss the new physical processes and evaluate the results.
We show that the determined albedo and climate in RACMO2 for the Greenland ice sheet now match better with in situ and remote sensing observations. Furthermore, the surface mass balance and energy budget are in good agreement with observations, with some mass balance changes at the margins. An important improvement is that absorption of sunlight beneath the surface leads to internal heating and therefore to higher snow temperatures. For the Antarctic ice sheet, sensitivity experiments illustrate that the modeled temperature and snowmelt are exceptionally sensitive to changes in the snowpack. To summarize, the introduction of more physical processes and the implementation of a new snow albedo scheme in RACMO2 has led to many new insights and a positive impact on the quality of model simulations.