Environmental Forcing of Ambient Noise in the Nansen and Amundsen Basins of the Arctic Ocean
NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF OCEANOGRAPHY
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The AREA 1992 experiment inserted three ANMET buoys on separate ice floes about 600 km north of Franz Josef Land. The buoys drifted in unison for most of the experiment and provided 12-19 months of hourly ambient noise data between 5 and 4000 Hz while obtaining limited weather data. The drift pattern was neatly divided into five legs of nearly uniform ice velocities in response to major changes in the wind field. The annual median spectra of each buoy were nearly identical at or above 200 Hz but diverged below 200 Hz. The largest differences were recorded between the two closest buoys. The annual spectra were 10 dB greater than the long term Eurasian Basin median spectra at all frequencies. The annual median spectra was 6-7 dB greater than the CEAREX 1988 1989 median spectra below 100 Hz but was quieter than CEAREX above 100 Hz. Ice speed was the best environmental correlate with ambient noise from 5-10 Hz, wind speed was best from 32-100 Hz, and wind stress was best above 100 Hz. Three periods of extreme noise levels two loud, one quiet, each lasting for several days, were investigated in detail to establish the role of wind forcing on ambient noise generation. Periods of loud noise were associated with periods of high windice speed coupled with rapid changes in direction, i.e., loud noise levels are the result of large ice convergence and shearing moment. Quiet periods occur when the buoy drift speed is slow. One of the loud noise events showed the periods of ice convergence on nearby land will increase the noise level, even during times of moderate wind speeds.
- Physical and Dynamic Oceanography