ASA 126th Meeting Denver 1993 October 4-8

2aAO8. Numerical modeling of long-range low-frequency propagation in irregular Arctic waveguide.

A. N. Gavrilov F. I. Kryazhev V. M. Kudryashov

N. N. Andreyev Acoust. Inst. and Ocean Acoust. & Inform. Ltd., 38 Vavilov St., Moscow, 1179542 Russia

An improved model of the Arctic ice cover and the mode coupling approach have been used for numerical calculations of low-frequency sound propagation over the irregular trans-Arctic paths proposed for acoustic monitoring of Arctic climate change. The ice cover was represented by a rough elastic layer with the roughness statistically determined by its spatial spectrum and correlation between the upper and lower ice surfaces. Horizontal change of the ice statistics along the supposed paths was approximated by a step function in accordance with existing data. The bottom relief and horizontal variation of the typical sound speed profile were approximated by segment-linear functions. In the ice modeling particular attention has been given to the influence of the ice cracks on low-frequency propagation loss. This can be regarded as a shear wave attenuation in the broken ice plate which differs strongly from shear wave absorption in normal ice and mainly depends on a mean size of the ice fields. Calculated acoustic propagation loss over the trans-Arctic paths differ from the empirical to experimental data after a 1000-km distance, with the calculated loss significantly less than the empirical prediction. This is caused by a relative increase of the deep-water mode contribution to the total sound field at such long distances.