Development of a Sea-Ice Penetrometer

Abstract

Introduction For the past several years the U. S. Coast Guard has pursued a research and development program intended pursued a research and development program intended to lead to the ability to reconnoiter large expanses of sea ice by fixed-wing aircraft without hindrance by weather or darkness. This capability is necessary if our country is to exploit the natural resources of our northern regions. A key requirement for our reconnaissance capability is the ability to measure the thickness of the sea ice from the air, since the thickness is a major determinant of its trafficability. Sea ice is a complex medium that is virtually impossible to duplicate in the laboratory. In addition, its properties conspire to frustrate most techniques for the remote measurement of its thickness. Numerous techniques have been investigated for remotely measuring sea-ice thickness, most without success. Sonic sounding has been tried by numerous investigators, but the high signal attenuation, poor signal-to-noise ratio, and indistinct ice-water boundary has defeated almost all experiments of which we are aware. Likewise, most methods involving electromagnetic radiation have been unsuccessful, although one or two ideas have begun to show some promise. (It should be pointed out that fresh ice, such as forms on the Great Lakes, while possessing certain complexities of its own, is more amenable to remote measurement than sea ice.) Considering the above, the Coast Guard's Office of Research and Development decided to fund the development of some approach radically different from the sonic and electromagnetic techniques we have mentioned. Since drilling is the only technique for measuring the thickness of sea ice that is accepted without reservation by the community, the first thought was "lets drop something on the ice, have it drill a hole, measure the thickness, and radio it up to us in the aircraft." JPT P. 249