Vibrational Motion of Arctic Pack Ice

• Main Authors: Dugan, John, Morris, William, Williams, Zandy
• Other Authors: ARETE ASSOCIATES ARLINGTON VA
• Format: Text
• Language: English
• Published: 1997
• Subjects: Snow; Ice and Permafrost; Acoustics; *GEOACOUSTICS; *AMBIENT NOISE; *PACK ICE; VIBRATION; ELECTROMAGNETIC WAVE PROPAGATION; ICE FORMATION; UNDERWATER ACOUSTICS; GRAVITY WAVES; NOISE MODULATION; ICE BREAKUP; GEOPHONES; Arctic; Ice; permafrost
• Online Access: http://www.dtic.mil/docs/citations/ADA329604; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA329604

There are many physical mechanisms responsible for vibrations of sea, and they force motions in a very wide band of frequencies from less than 0.01 Hz to greater than 100 Hz. Detailed measurements of the vertical velocity in this frequency band were previously shown to be produced by gravity waves, ridging events and wind turbulence. In this paper, higher frequency motions as measured by geophones for frequencies up to about 1 kHz have been analyzed, and the motions are identified as being generated by ridging events, thermal fracturing, and wind blown ice crystals. The sensors were frozen into the top surface of the ice, and they provided direct measurements of the vertical velocity that occurs in response to the different modes of waves that propagate away from these generation regions. The shape of the frequency spectrum is shown to be a strong function of the forcing mechanism, with the different ones being readily identifiable.