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

This article investigates the fission and evolution of internal solitary waves (ISWs) propagating over gentle continental shelves, focusing on the shelf region beyond the slope—a less-studied area in prior research. Using high-resolution numerical simulations based on the variable coefficient adjusted high-order unidirectional (vaHOU) model, validated against laboratory experiments, the study identifies critical thresholds for wave splitting: significant fission occurs when the normalized wave amplitude (|a|/h₁) is at least 0.5 and the bottom slope (S) is at least 0.4. The number of fissioned waves stabilizes at a maximum of 17 due to energy redistribution constraints, and this behavior is quantitatively described by an exponential saturation model relating wave amplitude and slope steepness. These findings enhance understanding of ISW dynamics over gentle shelves and provide a predictive framework relevant to energy redistribution and mixing in stratified coastal environments.