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In confined stratified basins, wind forcing is an important mechanism responsible for the onset and generation of internal waves and seiches. Previous observations have also found that gravity currents in stratified environments can also initiate internal waves. We conducted a series of laboratory experiments to investigate the generation of internal motions due to such dense gravity currents on an incline entering a two-layer stratification, focusing in particular on the interaction between the onset of internal motions and topography and diapycnal mixing due to breaking internal waves. The baroclinic response of the ambient stratification to the gravity current is found to be analogous to a system forced by a surface wind stress, and the response as characterized by a Wedderburn-like number was found to be linearly proportional to the initial gravity current Richardson number. The generated internal motions are characterized as having a low-frequency internal surge and higher-frequency progressive internal waves. The overall mixing efficiency of the breaking internal wave was calculated and found to be low compared with similar previous studies. 

A series of laboratory experiments were conducted to investigate the characteristics of a dense gravity current flowing down an inclined slope into a quiescent two-layer stratification. The presence of the pycnocline causes the gravity current to split and intrude into the ambient at two distinct levels of neutral buoyancy, as opposed to the classical description of gravity currents in stratified media as being either a pure underflow or interflow. The splitting behaviour is observed to be dependent on the Richardson number ( $$Ri_{\unicode[STIX]{x1D70C}}$$ ) of the gravity current, formulated as the ratio of the excess density and the ambient stratification. For low $$Ri_{\unicode[STIX]{x1D70C}}$$ , underflow is more dominant, while at higher $$Ri_{\unicode[STIX]{x1D70C}}$$ interflow is more dominant. As $$Ri_{\unicode[STIX]{x1D70C}}$$ increases, however, we find that the splitting behaviour eventually becomes independent of $$Ri_{\unicode[STIX]{x1D70C}}$$ . Additionally, we have also identified two different types of waves that form on the pycnocline in response to the intrusion of the gravity current. An underflow-dominated regime causes a pycnocline displacement where the speed of the wave crest is locked to the gravity current, whereas an interflow-dominated regime launches an internal wave that moves much faster than the gravity current head or interfacial intrusion.