Generation and propagation of internal tides and solitary waves at the shelf edge of the Bay of Biscay

Abstract

AbstractHigh‐frequency mooring data were collected near the northern shelf edge of the Bay of Biscay to investigate the generation and propagation of internal tides and internal solitary waves (ISWs). During spring tide, strong nonlinear internal tides and large amplitude ISWs are observed every semidiurnal tidal period. While onshore propagation was expected since the mooring is located shoreward of the maximum internal tidal generation location, both onshore and seaward traveling internal tides are identified. Within a tidal period at spring tide, three ISW packets are observed. Like internal tides, different ISW packets have opposite (seaward and shoreward) propagating direction. Based on realistic hydrostatic HYCOM simulations, it is suggested that advection by the barotropic tide affects wave generation and propagation significantly and is essential for the seaward traveling internal tides to appear shoreward of their generation location. A two‐layer idealized nonhydrostatic model derived by Gerkema (1996) further confirms the effect of advection on the generation and propagation of internal tides. Moreover, the two‐layer model reproduces one seaward propagating ISW packet and one shoreward propagating ISW packet, indicating that the offshore and onshore traveling ISWs are excited by nonlinear steepening of the seaward and shoreward traveling internal tides, respectively.