Inversion of Absorption Coefficient Profile with SSP and Argo Salinity Model for Precise Backscatter Processing

Multibeam backscatter data are important for marine resource exploration and benthic habitat mapping. However, accurate estimation of absorption loss without concurrent CTD measurements can be challenging. This paper proposes an inversion method that combines a global Argo salinity model with sound speed profiles (SSPs). The method enables absorption loss correction using only SSP data, offering a potential engineering alternative that reduces the need for dedicated CTD casts and may support real-time processing. Salinity is interpolated from the Argo grid, temperature is inverted via empirical formula for sound speed, and the absorption coefficient is computed using the Francois–Garrison model. The method is evaluated using two open-access multibeam datasets from the NCEI: one from the Blake Plateau (depth 1050–1250 m, 26.5 kHz) and another from Johnston Atoll (depth 2000–5000 m, 28 kHz). Compared to concurrent CTD profiles, the maximum deviations observed are 0.3 ppt for salinity, 0.1 ∘C for temperature, and 0.06 dB/km for absorption coefficient. The difference in absorption loss between the inversion and the CTD-based reference is within 0.1 dB. A precomputed lookup table indexed by incidence angle and one-way travel time is constructed for rapid estimation. In a test of 5196 swaths (432 beams per swath), the total interpolation time is 0.726 s. These results suggest that the proposed method provides a practical solution for absorption loss correction when CTD data are unavailable.