A Numerical Model of Tides in the Cretaceous Seaway of North America

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Abstract
A numerical model of the tides in an idealized Cretaceous Seaway of North America is used to calculate the lunar semidurnal tide for a variety of possible values of controlling parameters. The most important parameters are the bathymetry and boundary conditions. Since the bathymetry of the Seaway is not well known, it suffices to use uniform-depth models. Separate runs are made for depths of 100, 200 and 600 m in a completely closed basin. The largest response is for the 200 m depth, because of a resonance of the Seaway at 211 m. Five additional runs are made for a depth of 200 m and different combinations of tidal forcing, according as the tidal force acts directly on the Seaway (independent tide) or indirectly through the Seaway''s possible connection with the Arctic Ocean or Gulf of Mexico (co-oscillating tides). The independent tide accounts for the majority of the response of the Seaway. This is the opposite of modern marginal seas where the co-oscillating tide predominates. The co-oscillating tide from the Arctic Ocean is very small compared with the independent tide, but the co-oscillating tide from the Gulf of Mexico can be significant. If the Gulf of Mexico is not tidally connected with the Seaway, a radiation condition along the southern boundary is appropriate. This reduces the independent tide of the Seaway by .apprx. 20%. The most realistic run combines a northern boundary open to the Arctic Ocean, an independent tide in the Seaway, and a radiation condition on the southern boundary. The maximum range of the tide elevation that results is 86 cm; the maximum current speed is 10 cm s-1.