Radio Echo Studies of Glaciers
There is a need for measurements of the thickness of glaciers, ice sheets, and ice shelves. Radio waves propagating in naturally occurring ice masses are attenuated by absorption in the conducting medium, by reflection from discontinuities, and by scattering from inhomogeneities. These scattering centres nay be impurities, free water, or solid ice within less dense firn. A v.h. f. radar system has been designed specifically to produce continuous profiles of ice thickness when used either on the surface of a glacier, or in an aircraft flying over it. The frequency dependence of the attenuation mechanisms influences the choice of radio frequency used by the echo sounder. Electronic control and annotation circuits have been developed for use in the echo sounder and its data recording system, to simplify field operation and avoid errors caused by mistakes in manual recording and annotation. The author has tested the equipment on glaciers in Norway and in the Antarctic, where extensive measurements of ice thickness have been made both in Eastern Antarctica and in the Antarctic Peninsula. Information about glacier temperature and structure, and about the nature of the subglacial media, is also obtained. Measurements of ice thickness made from an aircraft, require navigational data to be used to determine the location of measurements. A digital computer has been used to analyse the available aircraft flight parameters and other navigational information, and to produce position coordinates which are collated with thickness measurements. Consideration has been given to the effect of random and systematic errors in the measurements, on the informtion obtained. Methods of presenting the measurements, which are distributed along flight lines, have been explored. An algorithm has been developed to produce contour naps of such measurements, with particular application to computer methods.