Dynamics of gravity currents under external and internal stratification in geophysical systems

Gravity currents play an important role in various geophysical processes and practical applications. However, the dynamics of these density-driven flows are significantly affected by external and internal density stratification conditions. This review provides a comprehensive analysis of the dynamic characteristics of gravity currents under different stratification regimes, focusing on propagation speed, bottom separation, turbulent mixing, entrainment mechanisms, and the excitation of internal waves. By synthesizing results from laboratory experiments, numerical simulations, and theoretical analysis, we discuss how external and internal stratification conditions influence the dynamic behavior of gravity currents. Research findings consistently show that ambient stratification suppresses the propagation speed, energy conversion, turbulent mixing, and entrainment mechanisms. However, interactions between gravity currents and internal waves result in current splitting and decapitation, significantly altering the flow structure and mass transport in stratified environments. By integrating insights from multiple studies, this paper highlights key research advances and provides a structured framework for understanding the fundamental and applied aspects of gravity current dynamics in density-stratified environments. It identifies knowledge gaps and recommends future research directions.