Relationships Between L-Band Brightness Temperature, Backscatter, and Physical Properties of the Ross Ice Shelf Antarctica

Radiometric and radar data from NASA's Soil Moisture Active Passive (SMAP) satellite are presented in a study of the Ross ice shelf, Antarctica. L-band brightness temperature ( $T_{B}$ ) patterns compare favorably to the outflow patterns from East and West Antarctica. Cooler $T_{B}$ is associated with the broad outflow from West Antarctic ice streams and the outflow from narrow outlet glaciers that drain East Antarctica. Aside from outlet glacier discharges, ice from East Antarctica is thinner and radiometrically warmer than that from West Antarctica. $T_{B}$ is stable across the ice shelf over the 6-year period of observations (1-2 K standard deviation). Over shorter times, surface melt events cause pre- and post-melt TB to vary by as much as 5 K in vertical polarization. Radar measurements highlight areas where backscatter is strong from melt-related ice lenses and ice layers, consistent with a corresponding decrease in TB. The TB polarization ratio on the ice shelf is approximately 1.13 and decreases from the West Antarctic grounding line toward the East Antarctic outlet glaciers. The backscatter polarization ratio increases by several dB from West to East Antarctica, indicating a decreasing influence of volume scatter toward East Antarctica. The decreasing TB polarization ratio indicates a diminishing role of firn layering on the depth-integrated emission. There is a negative correlation between warming brightness temperature and thinning. An explanation for this observation is that the relatively warm ice shelf has a relatively shallow (500 m or less) penetration depth leading to a warm physical temperature bias.