Statistical characterization of the geophysical and electrical properties of snow on Landfast first‐year sea ice

Abstract

In this work we quantify the vertical geophysical and electrical properties of a snow cover on landfast first-year sea ice observed during the Seasonal Sea Ice Monitoring and Modelling Site (SIMMS'92) experiment. Snow grain morphology, density, salinity, temperature and wetness were measured; the volume fractions of air, ice, brine, and the complex dielectric constant of the snow were modeled over a 3-cm vertical resolution spanning a seasonal period from April to June. Our results show that over the vertical dimension the snow grain morphology, salinity, density, and fractional volumes of brine, ice, and air covary. The statistical characterization of the vertical grain morphology indicates that two distinct layers occurred under cold (-20øC) and three layers under warm (-5øC) atmospheric temperatures. Over the seasonal period it was shown that new snow was deposited at about 250 kg.m -3 and quickly compacted to 375 kg.m -3' Snow grains grew at different rates within the snow cover because of differing metamorphic conditions. Dielectrically, the snow volume followed closely the seasonal and vertical patterns of grain morphology, salinity, temperature, density and the phase proportions of water within the snow volume. As the season evolved, the increasing brine volumes and presence of water in liquid phase caused the dielectric properties to increase over several factors (e•ix) and orders of magnitude introduction Snow has received the vast majority of scientific inquiry when it occurs over a land cover type, rather than over a sea ice volume. Of the studies which have been conducted on a sea ice snow cover [e.g., Matzler et al., 1984a; Kim et al.

Sea ice thickness, freeboard, and snow depth products from Operation IceBridge airborne data

“…As shown by it is necessary to discard data collected with warm surface temperatures due to the presence of liquid water, which changes the dielectric properties of the snow pack. Similar to the study of , we discard data when the surface temperature is greater than -5 • C, this is the temperature threshold identified in observations by Barber et al (1995) where large dielectric changes in the snow pack begin to take place. When available, the surface temperature is determined from the IceBridge KT-19 infrared radiation pyrometer data set (Shetter et al, 2010).…”

Ku-, X- and C-Band Microwave Backscatter Indices from Saline Snow Covers on Arctic First-Year Sea Ice

“…Field measurements from the three snow thicknesses show a highly saline bottom 4 cm basal layer (~6-~20 parts per thousand (ppt)) consisting of somewhat-rounded depth hoar crystals (Tables 1-3). High salinities in the basal snow layers are due to significant upward brine wicking [16,23,24]. The presence of brine throughout the snow cover during the late winter season are less commonly observed as snow covers are brine-wetted usually during freeze-up, and snow covers overlaying highly saline frost flowers.…”

“…Post-measurement destructive snow sampling (including snow thickness and thermophysical measurements) of the scatterometer scan area revealed that the snow cover was consistent with the adjacent snow pit used for sampling snow thermophysical measurements. However, it has to be noted that stochastic variability in snow thermophysical properties from a single snow cover from different snow pits located within small spatial scales may exist [16]. This study also assumes the air/snow interface and within-snow interfaces to be radar smooth [14].…”

“…The presence of brine throughout the snow cover during the late winter season are less commonly observed as snow covers are brine-wetted usually during freeze-up, and snow covers overlaying highly saline frost flowers. [16,23].…”

“…With changes in snow thickness and its associated thermophysical properties such as snow temperature, snow salinity, snow density and snow grain size (grain radius or specific surface area) on FYI, microwaves exhibit characteristic variations within different snow cover types on FYI [15,16]. Snow cover can influence and modify microwave interactions on FYI (dependent on incidence angle (θ inc ), polarization and wavelength) in two ways.…”