## 3 Results and Discussion
### Comparison Results of TL Calculations  
The BELLHOP ray model was used to calculate the TL of our model and the actual KEF environment. Compared with the normal mode model or parabolic equation model, the ray model can clearly describe the change of sound energy in the process of propagation, which is more suitable for the ocean front environment in this paper. The parameter settings in the sound field calculation process are as follows: the sound source frequencies were set to 50 Hz and 400 Hz, the glancing angle was \(-20^{\circ}\)-\(20^{\circ}\), the sound source depth (SD) was 100 m, 300 m, and 500 m, and the receiving depth remained the same as the SD. The seabed sound speed is 1600 m/s, the density was 1.8 g/cm\({}^{3}\), and the sound absorption coefficient of the seabed was 0.8 dB/\(\lambda\). We respectively calculated the TL under the model environment and the actual ocean front environment at different times (Figures 9-12). We found that when the SD was 100 m, the difference between the TL calculated by the model and the TL calculated by the actual \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Date**} & **Starting Position of** & **Ending Position of** & **The Width of Frontal** & **Melt Parameter (a)** \\  & **Frontal Zone (km)** & **Frontal Zone (km)** & **Zone (km)** & **Melt Parameter (a)** \\ \hline
0101 & 100 & 150 & 30 & 0.2 \\
0201 & 110 & 160 & 60 & 0.3 \\
0701 & 70 & 120 & 50 & 0 \\
0801 & 50 & 130 & 70 & \(-0.1\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Detection results of the frontal zone via FCM and selection of melt parameters at different times at 144\({}^{\circ}\) E section. Figure 8: The model of the sound speed field of the KEF (0–2000 m): (**a**) 1 January 2019; (**b**) 1 February 2019; (**c**) 1 July 2019; (**d**) 1 August 2019. The distribution of sound speed obtained by the overall model was similar to that of the actual KEF (Figure 2) in terms of the location of the front and the depth of the influence (especially in winter). Because only two typical water mass sound speed profiles and the location information of frontal zone was extracted as input in our model, the results of the model are still different from the actual distribution of the sound speed of the ocean front in detail. ocean front was very small at low and high frequencies. The result of the model at 100 m can well replace the actual TL; at 300 m, only on February 1 st (Figure 10b,e), the calculation results of low frequency and high frequency showed a small difference after passing the frontal zone, but in terms of the overall distribution trend, the results of the model were similar to the calculation results under the actual ocean front environment; at a deeper emission depth (SD = 500 m), since the SD is close to the SOFAR axis, there was no obvious convergence area or shadow area phenomenon in the distribution of TL, but in terms of the overall trend, the results of the model and the actual results also showed many similarities. Figure 9: Comparison of the model and actual TL under different SD and frequency on 1 January: (**a**) f = 50 Hz, SD = 100 m; (**b**) f = 50 Hz, SD = 300 m; (**c**) f = 50 Hz, SD = 500 m; (**d**) f = 400 Hz, SD = 100 m; (**e**) f = 400 Hz, SD = 300 m; (**f**) f = 400 Hz, SD = 500 m. When the SD was 100 m, the difference between the TL calculated by the model and the TL calculated by the actual ocean front was very small at low and high frequencies. At 300 m, in terms of the overall distribution trend, the results of the model were similar to the calculation results under the actual ocean front environment. At 500 m, in terms of the overall trend, the results of the model and the actual results also showed many similarities.