Fission dynamics and post-slope evolution of nonlinear internal waves over gentle continental shelves

This study explores the fission and evolution of internal solitary waves (ISWs) propagating over gentle continental shelves, with particular focus on the shelf region beyond the slope–an area often overlooked in prior studies. High-resolution numerical simulations based on the improved variable coefficient adjusted high-order unidirectional model, a simplified two-layer fluid framework validated against laboratory experiments, reveal critical thresholds for wave splitting, where significant fission occurs for wave amplitudes |a|/h1≥0.5 and bottom slopes S≥0.4. A novel nonlinear saturation model is developed to quantitatively describe the relationship between the number of fissioned waves, wave amplitude, and slope steepness, capturing the observed stabilization of Nmax due to energy redistribution constraints. These findings bridge a critical gap in understanding ISW dynamics in post-slope shelf regions and offer a predictive framework applicable to natural oceanic conditions. The validated model enhances insight into energy redistribution, sediment transport, and ecological processes in stratified coastal environments.