3pUW4. A predictive model for underwater noise level variations with an application to the fracturing of sea ice.

Session: Wednesday Afternoon, December 4

Time: 2:40

Author: James K. Lewis
Location: Ocean Phys. Res. & Dev., 207 S. Seashore Ave., Long Beach, MS 39560
Author: Peter J. Stein
Location: Science Solutions, Inc., Hollis, NH 03049
Author: Steve E. Euerle
Location: Science Solutions, Inc., Hollis, NH 03049


A model of the thermal fracturing of the sea is coupled with a model of acoustic propagation in ice and the underlying water to provide a means of predicting underwater noise variations with time. Numerical simulations using the ice-fracturing model provides a time history of the number of fractures per time step, as well as the location of the fracture relative to the surface of the ice. An analytical model is presented that relates such fracturing within an ice floe to noise levels at a given frequency in the water column under the ice. This model accounts for temporal and spatial variations of the elastic modulus of the ice. The analytical solution predicts that most thermally induced, under-ice noise at 500 Hz is a result of fracturing occurring between 5 and 25 cm below the ice surface for a 1.6-m-thick piece of sea ice. When used in conjunction with the fracture time histories determined by the rheological model, the under-ice noise levels predicted by the analytical solution compare quite well with noise observations in the eastern Arctic Ocean.

ASA 132nd meeting - Hawaii, December 1996