Summer Antarctic sea ice as seen by ASAR and AMSR-E and observed during two IPY field cruises: a case study

Abstract

AbstractEnvisat Advanced Synthetic Aperture Radar (ASAR) Wide Swath Mode (WSM) images are used to derive C-band HH-polarization normalized radar cross sections (NRCS). These are compared with ice-core analysis and visual ship-based observations of snow and ice properties observed according to the Antarctic Sea Ice Processes and Climate (ASPeCt) protocol during two International Polar Year summer cruises (Oden 2008 and Palmer 2009) in West Antarctica. Thick first-year (TFY) and multi-year (MY) ice were the dominant ice types. the NRCS value ranges between –16.3 ± 1.1 and –7.6 ± 1.0 dB for TFY ice, and is –12.6 ± 1.3 dB for MY ice; for TFY ice, NRCS values increase from –~15 dB to –9 dB from December/January to mid-February. In situ and ASPeCt observations are not, however, detailed enough to interpret the observed NRCS change over time. Co-located Advanced Microwave Scanning Radiometer–Earth Observing System (AMSR-E) vertically polarized 37 GHz brightness temperatures (TB37V), 7 day and 1 day averages as well as the TB37V difference between ascending and descending AMSR-E overpasses suggest the low NRCS values (–15 dB) are associated with snowmelt being still in progress, while the change towards higher NRCS values (–9 dB) is caused by commencement of melt– refreeze cycles after about mid-January.