## 4 Discussion  
In this study, we evaluated the influence of sound absorption coefficients on MBES backscatter calibration in the East Sea of Korea. The results demonstrated that spatiotemporal variations in absorption coefficients arise due to seasonal and regional differences, driven by dynamic oceanographic processes such as cold currents and distinct water masses. By integrating site-specific parameters into the calibration workflow, we addressed these variations and improved the consistency of the calibrated backscatter data. Specifically, Site A--where the spatial and temporal discrepancies between SVP and historical KODC measurements were minimal--showed better agreement in the calibrated results. However, for  
Figure 8: MBES data and SVP-based calibration results at Site C: (**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. Sites B and C--where the spatial and temporal differences were more pronounced--greater discrepancies in backscatter intensity were observed [5; 6; 7]. The integration of SVP and historical CTD datasets enabled the calculation of sound absorption coefficients and re-processing of legacy MBES data. While historical CTD datasets provide a valuable resource for understanding long-term trends, they are constrained by physical limitations, such as the lengthy time required for data collection and processing. Similarly, SVP measurements also face certain physical limitations but offer more favorable conditions when compared with CTD datasets. SVP data are more practical for coastal surveys, due to their ease of acquisition and frequent availability, allowing for calibration of MBES datasets compared with the more resource-intensive CTD measurements. This distinction highlights the complementary role of SVP data in addressing some of the challenges associated with the sole use of CTD data in dynamic marine environments. This study, while focusing on a specific case in the East Sea of Korea, provides valuable insights into the calibration of MBES backscatter data with the sound absorption of the water column in various oceanic environments. The differences in backscattered intensity between legacy MBES data and the data calibrated for the water column absorption, based on SVP and CTD data, may appear modest at up to 2.1 dB. However, these differences are significant when considered in the context of deeper waters operating at lower frequencies. Previous studies on absorption loss uncertainties have demonstrated that as operating frequencies decrease in deep oceans, particularly at 30 kHz, the impact of absorption loss becomes more pronounced [7]. For example, the maximum absorption loss uncertainty is 3.3 times greater in deep waters at 30 kHz compared with shallow waters at 300 kHz, illustrating a substantial amplification of uncertainty with greater depth and lower frequency. Expanding this methodology to other ocean environments with diverse oceanographic conditions would further validate its applicability and provide broader insights into MBES calibration practices. Other studies have suggested frameworks for quantifying uncertainties in seafloor acoustic backscatter, which could serve as a reference for improving error estimates in calibration processes [29; 30]. While this study primarily focused on evaluating spatiotemporal variations in sound absorption coefficients, we acknowledge the absence of a comprehensive sensitivity analysis as a limitation. Future work should include error budgets or uncertainty quantifications for the absorption parameters derived using models such as the Francois-Garrison formulation.