Multi-Frequency Measured and Modeled Microwave Backscatter from a Highly Saline Snow Cover on Smooth First-Year Sea Ice

Abstract:

Monitoring Arctic sea ice and its snow cover variability is of prime importance in Cryosphere research. Snow cover plays major roles in the energy balance of Arctic sea ice and also required to understand the present condition and future behavior of first-year ice (FYI). Microwave remote sensing provides the most effective means to acquire near-real time thermodynamic information about snow cover on smooth FYI. Microwave interaction with snow-covered sea ice is a function of both snow and ice electro-thermo-physical properties such as shape, size and orientation of scatterers, surface roughness, complex dielectric constant as a function primarily of brine volume, and brine volume as a function of temperature, salinity and density; as well as microwave parameters such as incidence angle, polarization and wavelength. Fluctuations in snow cover thermodynamics affect microwave propagation, attenuation, and scattering through the influence that brine volume exerts on interfacial and volume characteristics of snow and ice layers. Previous studies exhibit reduced penetration depth and inaccurate snow thickness estimates, using a single-frequency approach (C-band), from highly saline snow covers. We present a case study based on an observational (Ku-, X- and C-band surface-based fully-polarimetric microwave scatterometer system) and theoretical multi-frequency approach (using first-order microwave scattering and penetration depth models), to understand the sensitivity of varying snow thermodynamics on microwave scattering and penetration. The study site is a 14cm highly saline snow cover over smooth FYI, near Resolute Bay, Nunavut, Canada (Figure 1), with in-situ snow property measurements acquired from 18th to 20th May 2012, when snow layer temperatures were found to be fluctuating (Figure 2). Preliminary results show variations in observed Ku-, X- and C-band VV backscatter (Figure 3) and penetration (Figure 5) for warm (18th and 20th May) and cold (19th May) snow cases, similar to the modeled VV backscatter (Figure 4). Based on our initial observations, the thermal dependence of multi-frequency microwave backscatter over highly saline snow on FYI shows promise to provide an initial foundation to understand their microwave interactions necessary for snow thickness estimation on FYI.