We examine how low-frequency variations in adjusted sea level over a continental shelf are influenced by an inland sea connected to the shelf through a strait. An analytical model shows that free continental shelf waves propagating by the mouth of the strait are strongly modified at a period corresponding to a Helmholtz-like resonance of the inland sea and strait. Also, near this period atmospheric pressure variations over the inland sea result in relatively strong flow through the strait, and the resulting cross-isobath flow over the exterior shelf efficiently generates continental shelf waves in the region forward of the strait. Calculations using a fully nonlinear numerical model with more realistic, although still idealized topography verify the predictions of the simpler analytical model. We apply this theory to the Hudson Bay-Labrador Shelf system where we find that this mechanism of shelf wave generation strongly influences the shelf response in the energetic meteorological band (~2--6 days). Data from the Nain, Labrador are analyzed using multiple linear regression models and lend further support to the theory. ¿ American Geophysical Union 1987