Snow depth distributions on sea ice of different ages and thicknesses from regional field campaigns

Abstract. Accurately representing the snow depth (SND) distribution on sea ice is essential for sea ice thickness (SIT) retrievals, ecological studies, and climate modelling. Using co-located SND and SIT measurements from multiple polar in-situ sea ice campaigns, this study examines sub-kilometre-scale SND variability and identifies the most suitable probability density function (PDF) to represent SND distributions across different ice ages and thicknesses. First, we examine the statistical properties of SND and their dependence on SIT, finding a linear increase in SND with SIT for first-year ice. The coefficient of variation (CV = standard deviation/mean SND) remains constant at 0.50 across all SIT regimes, allowing direct estimation of variability from mean SND. In particular, lower-than-expected SND variability was observed at flooded sites, where snow loading depresses the ice and allows seawater to infiltrate the snow, resulting in a reduced CV. Moreover, the results reveal differences in SND distributions across ice ages and SIT during winter and summer. Specifically, snow over younger ice has a shorter residence time and is best represented by a log-normal distribution, whereas progressive wind-driven redistribution shifts the SND towards a skew distribution. Accordingly, snow over older ice, which typically has a longer residence time, is better represented by a skew distribution. Notably, although the log-normal distribution performs best under specific conditions (e.g. new or melt-season snow), its performance can deteriorate substantially over older and thicker ice, whereas the skew distribution provides a robust representation across heterogeneous ice types. SND correlation lengths derived from semi-variograms show a positive relation with SIT and are enhanced by drifting snow events. These results underscore the importance of ice-condition-dependent parameterizations for representing sub-kilometre SND distribution and improve sub-grid-scale representations of SND variability in remote-sensing retrievals and climate models.