CP Climate of the Past CP 1814-9332 Copernicus GmbH Göttingen, Germany 10.5194/cp-7-277-2011 A regional ocean circulation model for the mid-Cretaceous North Atlantic Basin: implications for black shale formation Topper R. P. M. 1 Trabucho Alexandre J. 1 Tuenter E. 1 2 Meijer P. Th. 1 Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, The Netherlands 21 03 2011 7 1 277 297 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.clim-past.net/7/277/2011/cp-7-277-2011.html The full text article is available as a PDF file from http://www.clim-past.net/7/277/2011/cp-7-277-2011.pdf

High concentrations of organic matter accumulated in marine sediments during Oceanic Anoxic Events (OAEs) in the Cretaceous. Model studies examining these events invariably make use of global ocean circulation models. In this study, a regional model for the North Atlantic Basin during OAE2 at the Cenomanian-Turonian boundary has been developed. A first order check of the results has been performed by comparison with the results of a recent global Cenomanian CCSM3 run, from which boundary and initial conditions were obtained. The regional model is able to maintain tracer patterns and to produce velocity patterns similar to the global model. The sensitivity of the basin tracer and circulation patterns to changes in the geometry of the connections with the global ocean is examined with three experiments with different bathymetries near the sponges. Different geometries turn out to have little effect on tracer distribution, but do affect circulation and upwelling patterns. The regional model is also used to test the hypothesis that ocean circulation may have been behind the deposition of black shales during OAEs. Three scenarios are tested which are thought to represent pre-OAE, OAE and post-OAE situations. Model results confirm that Pacific intermediate inflow together with coastal upwelling could have enhanced primary production during OAE2. A low sea level in the pre-OAE scenario could have inhibited large scale black shale formation, as could have the opening of the Equatorial Atlantic Seaway in the post-OAE scenario.

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