Numerical Simulations of Productivity and Anoxia in the Western Interior Seaway During Oceanic Anoxic Event 2 (93.9 Ma)

Restricted (Penn State Only)
Author:
Clark, Brandon
Graduate Program:
Geosciences
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
October 26, 2018
Committee Members:
  • Lee Kump, Thesis Advisor
  • Bernd Haupt, Thesis Advisor
  • Elizabeth Ann Hajek, Committee Member
  • Timothy Bralower, Committee Member
Keywords:
  • Oceanic Anoxic Event 2
  • OAE2
  • Western Interior Sea
  • ROMS
  • Anoxia
Abstract:
We investigated the development of Oceanic Anoxic Event 2 (OAE2) at the Cenomanian/Turonian boundary (93.9 Ma) within the Western Interior Cretaceous Seaway (WIKS) of North America. In order to understand the conditions in the WIKS that led to basin anoxia, we conducted numerical simulations of the WIKS using a community oriented, high- resolution, eddy-resolving coastal ocean model, the Regional Ocean Modeling System (ROMS). This 3-dimensional ocean model allows for high resolution of benthic and surface layers by utilizing a vertical terrain following s-coordinate system. Our model is driven by atmospheric and surface ocean forcings from CCSM4, a global coupled Atmosphere-Ocean General Circulation Model (AOGCM) developed at the National Center for Atmospheric Research (NCAR). Our results show that Boreal water entered the basin along the eastern and western margin of the north part of the WIKS. Flow is enhanced on the western side forming a strong boundary current from surface to deep. Meanwhile Tethyan water entered the basin across the western margin of the southern part of the WIKS. These waters mixed and formed an anticyclonic gyre in the center of the basin freshening Tethyan water as they exited the WIKS as a southward flowing jet on the eastern edge of the basin. The dominance of oxygen-depleted, nutrient-rich Tethyan water caused the WIKS to become anoxic at depth during OAE2. Understanding how the WIKS responded to these environmental perturbations in a “greenhouse climate” provides an analogue for how the modern shallow ocean will respond to increasing anthropogenic carbon emissions.