# Characteristics of Low-Frequency Acoustic Wave Propagation in Ice-Covered Shallow Water Environment
## 1 Introduction  
In recent years, global warming has led to a decrease in the area of Arctic ice, which has caused the world's marine powers to pay unprecedented attention to the Arctic [1]. In order to meet the needs of energy and minerals, fishery resources and the ecological environment, tourism and transportation, climate change and national defense security in the Arctic, countries think highly of the research on the sound propagation characteristics of low-frequency signals in the Arctic. Therefore, scholars have studied the models and modeling methods of the Arctic region. [PERSON] [2] firstly considered the ice interface with ridge distribution as an infinite semi elliptical cylinder, which was randomly distributed on a rigid or free interface and established the Burke-Twersky (BT) model to describe the sound field under the ice. [PERSON] [3] analyzed the relationship between the reflection loss and the size, number, and distribution density of ice ridges at different frequencies on the basis of the BT model, and further studied the propagation loss under the ice using the ray theory. [PERSON] [4] proposed an improved BT model, and the solution is consistent with the experimental results from the polar region in the low-frequency range. In order to study the polar sound field with the more realistic polar model, the perturbation theory has been used to calculate the scattering coefficients of elastic modes [5]. [PERSON] [6, 7] used the wave number integration method and the perturbation theory to derive the low-frequency reflection loss at the interface of the elastic medium, and he calculated the sound propagation loss under the Arctic ice. [PERSON] [8] applied the elastic parabolic equation to polaracoustic for the first time and verified the accuracy of the method. [PERSON] [9] developed a full-field perturbation method to estimate the narrow-band long-range reflection caused by the roughness of the ice water interface. [PERSON] [10] compared the reverberation of the fluid model ice with that of elastic model ice for an upward refracted acoustic velocity profile, and he further considered the reverberation of the elastic seafloor with a nearly fluid mud layer. Previous research mainly focused on ice modeling and analysis methods to study whether they are suitable for polar acoustics.  
Different from research studies above, this paper further considers the influence of some specific factors on the sound propagation characteristics of polar sound field from the perspectives of the elastic seafloor and the low-frequency signal. Section 2 details the elastic parabolic equation method and the polar acoustic numerical model of ice-water-seafloor. The ice layer and the seafloor are regarded as elastic media in this model [11; 12]. The accuracy of the polar sound field model is verified in Section 3. Section 4 focuses on the sound propagation characteristics of the traditional polar sound field model from three aspects: ice thickness, seawater depth, and seafloor medium parameters, and it reveals the propagation law of low-frequency signals in a polar shallow water sound field.