## 3 Results
### Multibeam Echoosounder Calibration  
The MBES maps collected from Site A (situated in proximity to the KODC 102 line-04 point) were processed employing the sound absorption coefficients obtained from SVP data. Historical oceanographic parameters recorded in April 2010, including a salinity measurement of 34 psu and temperature of 9 \({}^{\circ}\)C, served as the basis for data calibration. During the survey, the temperature from SVP indicated a marginally elevated temperature of 9.4 \({}^{\circ}\)C and salinity of 34.2 psu, culminating in a maximum discrepancy of 1.68 dB per line when computing the difference between the calibrated MBES backscattered intensity and the original uncalibrated outcomes. Figure 6 elucidates these differences, delineating the fluctuations in depth, original data, and the consequential effects of calibration of sound absorption on the backscattering map. The difference between the unprocessed and calibrated backscattered intensity was low but varied across the mapping lines.  
Site B (located in proximity to the KODC 209 line-04 point) was subjected to a comparable data processing methodology, albeit with distinct variations in the environmental parameters. The map acquired from the MBES was initially calibrated using empirical measurements obtained in June 2019, which indicated a salinity level of 34.2 psu and a temperature of 9 \({}^{\circ}\)C. Nevertheless, the SVP recorded during the survey indicated a temperature of 10.6 \({}^{\circ}\)C, thereby necessitating modifications to the sound absorption coefficients. Following the application of these adjustments, the maximum deviation was reduced to 2.1 dB per line. Unlike Site A (Figure 6), Site B exhibited notable regional differences across the left, right, and central areas, highlighting variations in sound absorption across these sections. Figure 7 provides a comparative analysis of the depth profiles alongside the differences in sound absorption before and after the calibration process.  
For Site C (located near the KODC 208 line-02 point), the MBES seafloor map was calibrated utilizing SVP measurements from September 2016. Due to the absence of concurrent CTD measurements, empirical data from October 2016--indicating a salinity of 33 psu and a back-calculated temperature of 16 \({}^{\circ}\)C--were employed. The actual SVP data during the survey revealed a salinity of 34 psu and a temperature of 15.62 \({}^{\circ}\)C, necessitating further calibration to align with these parameters. This calibration achieved a reduction in sound absorption discrepancies by 1.92 dB, as illustrated in Figure 8, which contrasts the raw and calibrated MBES maps. Site C represents the largest and most extensively mapped area, with less pronounced variations across individual lines but regional differences in the right central region (35\({}^{\circ}\) 26\({}^{\prime}\)). Site C exhibited larger discrepancies, although the differences were less extensive than those observed at Site B (Figure 7).  
Figure 6: MBES maps and SVP-based calibration results at Site A: (**a**) Bathymetric map from MBES measurement with measurement points for water depth and SVP (black stars), (**b**) unprocessed legacy MBES backscattered map, (**c**) calibrated MBES backscattered map employing the sound absorption coefficient, and (**d**) differences between unprocessed legacy and calibrated backscattered values. Backscattering (BS) denotes the intensity of the backscattered signal (in dB) for the difference at each point.  
Figure 7: MBES data and SVP-based calibration results at Site B: (**a**) Bathymetric map from MBES measurement with measurement points for water depth and SVP (black stars), (**b**) unprocessed MBES backscattered map, (**c**) calibrated MBES backscattered map employing the sound absorption coefficient, and (**d**) differences between unprocessed and calibrated backscattered values. Backscattering (BS) denotes the intensity of the backscattered signal (in dB) for the difference at each point.