Spatial sound field variability and mode coupling during upslope propagation in a coastal wedge

Wedge-like shallow water modeling is often used for sound field propagation in near-coastal zones of oceans. The canonical model, which has an analytical solution and is used in many applications, assumes a constant sound speed in the water layer. Recently it was shown by Jiang, Zhang and Katnelson [JASA Express Lett. 3, 016001 (2023)], however, that the presence of a thermocline significantly changes the structure of the sound field when propagating downslope due to the emerging specific mode coupling. In this paper, the problem of the sound field in such a wedge is considered for upslope propagation. The sound field is constructed both using an expansion over adiabatic modes and a parabolic equation. It is demonstrated that the mode coupling arising due to local violation of adiabaticity leads to noticeable variability of the spatial distribution of the field, i.e., the field decomposition by modes. The results are illustrated by calculations using real parameters in shallow water.