Near-coastal iceberg distributions in East Antarctica, 50-145°E

Abstract

A survey of icebergs using satellite radar images has been made in the seasonal sea-ice zone of East Antarctica in the sector between longitudes 50°and 145°E. These data provide information on the spatial distribution and size statistics of icebergs near the coast in areas not often visited by shipboard observers, and close to their sources at ice shelves and glacier tongues. The icebergs are detcted and their dimensions extracted by analysis of the texture properties present in satellite images acquired with ERS-1 synthetic aperture radar during the austral winter. The minimum size of iceberg reliably detected and measured is 0.06 km2. A significant variation, by up to a factor of two, is found in the area of icebergs close to different sections of the coast, which suggests a characteristic size for different sources. The average value of the length-to-width ratio for icebergs in the whole population shows some variability with size. The probability of finding icebergs is greatest close to the coast, decreasing in general with distance from the coast, such that few icebergs were detected more than 160 km from the coast. In one sector about 85°E, icebergs are found to at least 550 km from the coast, which is consistent with the transport of icebergs northwards in this region by a branch of the westward-heading near-coastal current (East Wind Drift) which connects with the southern margins of the eastward-heading Antarctic Circumpolar Current.