Double-Duct Acoustic Propagation Characteristics over the Chukchi Plateau Under Partial Sea-Ice Cover

This study evaluates upper boundary representations for double-duct acoustic propagation under partial sea-ice cover over the Chukchi Plateau. Elastic ice reflection, ice-ridge scattering, sea-ice concentration, and wind–wave roughness are incorporated into a three-dimensional Bellhop framework. A concentration-weighted equivalent reflection coefficient combines a magnitude based on reflected energy with an assumed representative phase. Predictions are compared with measurements from four stations during the 2018 Chinese National Arctic Research Expedition at seven frequencies from 500 to 2000 Hz. The plane elastic ice layer model gives lower mean absolute errors (MAEs) than the Burke–Twersky model at 1.25 and 1.6 kHz, while their MAEs differ by only 0.004 dB at 2.0 kHz. Across 28 station–frequency comparisons, the overall MAEs of the free-surface, ice-covered, and equivalent interface models are 4.189, 2.905, and 2.802 dB, respectively. The equivalent interface model has the lowest pooled MAE, although the ice-covered model performs better at S21 and S22. The wind–wave coefficient, β=0.75, is calibrated using S11/S12 at 1 kHz and fixed before validation at S21/S22. Agreement after the wind–wave correction varies with frequency and propagation path. These results support the use of the equivalent interface approximation for the sampled Chukchi Plateau conditions, with performance varying among stations.