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The forces governing marine circulation of a meridional transcontinental seaway is explored with the Princeton Ocean Model. The Jurassic Laurasian Seaway, which connected the low-latitude Tethys Ocean with the Arctic Sea is modeled quantitatively. The global ocean is found to have a profound influence on seaway dynamics. A north-south density difference and hence sea level difference of the global ocean was probably the main factor in forcing the seaway flow. When the Tethys waters were the denser water, the net seaway flow was southward, and conversely, it was northward for denser Arctic waters. Marine bioprovincial boundaries and sediment data indicate that the seaway probably was dominated by Boreal faunal groups and reduced salinities several times in the Jurassic. The model results suggest that this can be explained by southward flowing seaway currents, which may have been related to an oceanic thermohaline circulation where no northern high-latitude deep convection occurred.

[1] We examine the effect of Late Miocene paleogeography on the circulation and water properties of the Mediterranean Sea by using an ocean circulation model. Results obtained for the past are compared to a control experiment with the present-day geometry. To focus on paleogeography, atmospheric forcing is always based on the present-day climatology. We seek insight that allows us to test ideas based on observations and to formulate new working hypotheses. The Late Miocene is examined first, since it represents an important stage in the evolution of the Mediterranean. The present-day model reproduces the main aspects of the surface to intermediate depth circulation and water properties. The model does not capture the deep circulation known to occur at present in both subbasins. When the subbasins are reconstructed to their Late Miocene shape (keeping intervening sills at present-day levels) the overall nature of the surface/intermediate depth circulation proves unaffected. The model, however, predicts intense deep circulation in the eastern Mediterranean, most likely due to the greater surface area of the reconstructed Adriatic Sea. Using the first paleoexperiment as a starting point several additional paleogeographical aspects are examined.