Thickness and Structure of Antarctic Sea Ice Measured by Drilling and Impulse Radar

Abstract

Sea ice thickness was profiled in investigating the internal structure of sea ice in August 1982 near Syowa Station, East Antarctica, by drilling and using an impulse radar system. In this connection, the anisotropic properties of sea ice were studied by rotating the radar antenna on the horizontal surface of ice around the vertical axis. Ice cores 155 cm long were drilled for analysis of their internal structure, which showed that a brine-soaked layer existed at the depth of 90 cm. This layer corresponded to an internal echo of very strong intensity at this depth that did not change during the rotation of the antenna. Meanwhile, a bottom echo gave maxima and minima approximately every 90 degrees of rotation of the antenna; this alternation is attributable to the structure of newly grown ice with the preferred c-axis Orientation. From these findings we consider that two types of sea ice covered the area near Syowa Station: one with a brine-soaked layer; the other without. Irregularities in shape of the bottom echo suggest that the sea ice plane was composed of accumulated small plates of sea ice.