CSDMS 2016 annual meeting poster SalikAndersRosing
Cretaceous Deepwater Formation: Processes and sensitivities
Courtney Harris, Virginia Institute of Marine Science Gloucester Point Virginia, United States. ckharris@vims.edu
Christian J Bjerrum, Centre for Cross-disciplinary Chalk Research, Department of Geosciences and Natural Research Management, University of Copenhagen Copenhagen , Denmark. cjb@ign.ku.dk
Abstract:
It has been hypothesized that the warm Cretaceous Greenhouse climate with higher sea levels led to the breakdown of shelf front breaks and a thinning of the well mixed Ekman layer in continental shelf seas. Such a thinning would mean that shelf seas would have a more stratified structure, similar to that of the open oceans. With warmer climate, evaporation on stratified continental shelf seas could cause cascading of dense, high-salinity coastal waters, forming the oxygenated deep waters and leading to contour following currents in the intermediate waters below the pycnocline. Seismic surveys of the Upper Cretaceous Chalk group of the North Sea region suggest that the shallow Chalk Sea in which the group was deposited was under the influence of such contour following currents.
In order to test the hypothesis that dense water formation and cascading were a mechanism for deep water formation and contour following current forcing in the Chalk Sea, we developed an idealized model of the sea. The model, which was first proposed at the 2015 CSDMS meeting, simulates hydrodynamic and sediment transport processes, and is forced by climatic conditions (wind direction and strength, surface freshwater flux, salinity and temperature) informed by GCM modelling of the late Maastrichtian. Sediment properties are derived from experimental values. Here we present the final model and a range of sensitivity studies to demonstrate the feasibility of our hypothesis.
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