Estimation of thin sea-ice thickness from NOAA AVHRR data in a polynya off the Wilkes Land coast, East Antarctica

摘要

Antarctic coastal polynyas are major areas of intense ocean–atmosphere heat and moisture flux, and associated high sea-ice production and dense-water formation. Their accurate detection, including an estimate of thin ice thickness, is therefore very important. In this paper, we apply a technique originally developed in the Arctic to an estimation of sea-ice thickness using US National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) data and meteorological data in the Vincennes Bay polynya off Wilkes Land, East Antarctica. The method is based upon the heat-flux calculation using sea-ice surface temperature estimates from the satellite thermal-infrared data combined with global objective analysis (European Centre for Medium-Range Weather Forecasts (ECMWF)) data. The validity of this method is assessed by comparing results with independent ice-surface temperature and ice-thickness data obtained during an Australian-led research cruise to the region in 2003. In thin-ice (polynya) regions, ice thicknesses estimated by the heat-flux calculation using AVHRR and ECMWF data show reasonable agreement with those estimated by (a) applying the heat-flux calculation to in situ radiation thermometer and meteorological data and (b) in situ observations. The standard deviation of the difference between the AVHRR-derived and in itudata is ～0.02 m. Comparison of the AVHRR ice-thickness retrievals with coincident satellite passivemicrowave polarization ratio data confirms the potential of the latter as a means of deriving maps of thin sea-ice thickness on the wider scale, uninterrupted by darkness and cloud cover.