Comparison of different rike formation models of Arctic sea ice with observations from laser profiling

Sea ice deforms under convergent and shear motion, causing rafting and ridging. This results in thicker ice than could be formed by thermodynamic growth only. Three different approaches to simulating the formation of pressure ridges in a dynamic-thermodynamic continuum model are considered. They are compared with and evaluated by airborne laser profiles of the sea-ice surface roughness. The respective characteristic of each of the three ridging schemes is (1) a prognostic equation for deformation energy from which ridge parameters are derived; (2) a redistribution function, shifting ice between two categories, level and ridged, combined with a Monte Carlo simulation for ridge parameters; and (3) prognostic equations for ridge density and height, resulting in the formation of ridged-ice volume. The model results show that the ridge density is typically related to the state of ice motion, whereas the mean sail height is related to the parent ice thickness. In general, all of the three models produce realistic distributions of ridges. Finally, the second ridging scheme is regarded as the most appropriate for climate modelling, while the third scheme has advantages in short-term sea-ice forecasting.