Short-Pulse Radar Investigations of Freshwater Ice Sheets and Brash Ice

• Main Authors: Arcone,S A, Delaney,A J, Perham,R E
• Other Authors: COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
• Format: Text
• Language: English
• Published: 1986
• Subjects: Snow; Ice and Permafrost; Active & Passive Radar Detection & Equipment; *RADAR; *SHORT PULSES; *SEA ICE; THICKNESS; WATER; WAVEFORMS; DIELECTRICS; REFLECTION; MOISTURE CONTENT; DIELECTRIC PROPERTIES; FRESH WATER; PROFILES; ICE; SIGNALS; SHEETS; ANTENNAS; VALUE; DISTORTION; BOTTOM; LOW FREQUENCY; FRAGMENTS; Ice; Ice Sheet; permafrost; Sea ice
• Online Access: http://www.dtic.mil/docs/citations/ADA172578; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA172578

Short-pulse radar profiles and waveform traces were recorded over natural, freshwater ice sheets and an artificially made, 1.6-m-diameter column of brash ice. The purpose was to study the feasibility of this type of radar to detect ice thickness, determine ice properties and distinguish ice forms. The radar utilized two antennas: one with a spectrum centered near 900 MHz and a second more powerful one near 700 MHz. Distinct top and bottom reflections from several ice sheets were produced by both antennas, but the value of dielectric permittivity calculated from the time of delay of the reflections varied between sheets as one ice sheet was ready to candle and contained free water. The brash ice distorted signals and allowed no discernible bottom return. The lower frequency antenna also gave returns from the lake bottom (separated from the ice bottom by about 1 m of water), which could allow ice thickness to be determined indirectly. The report concludes that these antennas can be used to determine sheet ice thickness and to supply information to help in the detection of brash ice. The water content of an ice sheet may also be estimated if independent studies show a correlation between dielectric permittivity and free water content.