An examination of the distribution of snow on sea‐ice

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Abstract
Snow on sea‐ice is an integral, yet poorly understood, component of the ocean‐sea‐ice‐atmosphere interface. Snow exerts a significant control on both shortwave and conductive fluxes due to its high albedo and low thermal conductivity. Parameters pertaining to snow distribution and/or thickness are hard to model and/or to measure using geospatial techniques. In terms of Arctic hydrology, we consider three aspects of snow important to understanding processes operating within the ocean‐sea‐ice‐atmosphere interface: i) the average magnitude of snow thickness on sea‐ice; ii) the spatial distribution of snow as a function of location and ice type; and iii) the seasonal evolution of both magnitude and distribution. In this paper we focus on the second aspect; distribution. The distribution patterns of snow over first‐year (FYI), multiyear (MYI) and rubble (RI) sea‐ice were evaluated at 15 sites, sampled during two years of field research in the Canadian Arctic. A geostatistical technique known as the variogram was used to model the statistical pattern of the snow distribution. The significance of different snow distribution patterns was then evaluated using a radiative transfer model under various snow and ice type distributions. Results of this study indicate that the variogram provided a good estimate of the type and change of spatial dependence of snow depths over various types of sea‐ice. Over FYI, the regular smooth ice topography produced a periodicity in the snow drifts which was best estimated using a wave (hole‐effect) theoretical variogram in combination with a Gaussian model. The more uneven ice topographies characteristic of MYI and RI produced a more irregular snow drift pattern. The most appropriate models were a combination of the spherical and Gaussian variogram models (MYI sites) or a single Gaussian model (RI sites). The nugget values of the variograms increased as the sea‐ice topography became more irregular (smooth FYI to large uplifted ice pieces in RI). This was attributed to the presence of snow drifts in the MYI and RI sites that were less than the sampling interval. Geometric anisotropy was present in all 15 sites, indicating a directional trend in the spatial continuity of the snow distribution patterns which we attribute to the prevailing wind direction during depositional storm events. The ramifications of the snow distribution as a function of ice type were illustrated by the transmission of photosynthetically active radiation (PAR) through the three ice types. As the ice topography becomes more irregular, the areally averaged transmission of PAR decreases, thereby illustrating the non‐linear nature of the relationship between PAR extinction and snow thickness. The findings of this case study suggest that by knowing the type of sea‐ice we can make predictions about the statistical pattern of the associated snow distribution. More importantly, the main finding suggests that this snow distribution pattern will dominate the areally averaged transmission of PAR across the ocean‐sea‐ice‐atmosphere interface.

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