Tracking the Paleocene-Eocene Thermal Maximum in the North Atlantic: A shelf-to-basin analysis with a terrain-following ocean model

Restricted (Penn State Only)
Author:
Hantsoo, Kalev Griffin
Graduate Program:
Geosciences
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
October 30, 2017
Committee Members:
  • Lee Kump, Thesis Advisor
  • James Kasting, Committee Member
  • Timothy Bralower, Committee Member
  • Bernd Haupt, Committee Member
Keywords:
  • biogeochemistry
  • Paleocene Eocene Thermal Maximum
  • ROMS
  • Regional Ocean Modeling System
  • Paleogene
  • Salisbury Embayment
  • ocean acidification
  • calcite saturation
  • paleoceanography
  • paleoclimatology
Abstract:
The Paleocene-Eocene Thermal Maximum (PETM), a transient greenhouse interval spurred by a large release of carbon to the ocean-atmosphere ca. 56 Ma, provides a geological point of comparison for anthropogenic carbon emission. However, while geochemical proxies and fossil assemblages offer insights into the continental shelf response to the PETM, existing ocean-atmosphere models of the PETM do not include accurate shelf and slope bathymetry. Model-proxy comparisons are of particular interest along continental margins, which are ecologically and biogeochemically critical environments. Here we present high-resolution simulations of the pre- and syn-PETM North Atlantic basin that include a resolved continental shelf along the eastern margin of North America in the Salisbury Embayment. We use the Regional Ocean Modeling System (ROMS), whose terrain-following coordinate system permits a new level of detail along continental margins while also capturing open ocean processes. Our model’s boundary conditions are drawn from existing models of the PETM. Under a carbon forcing consistent with a release of ~13000 PgC, the calcite saturation horizon rises to an average depth of 725 m in the North Atlantic. Concurrently, a regime of continental slope downwelling in the western North Atlantic weakens during PETM onset. On the continental shelf, benthic oxygen concentrations decrease by 32.5% with seasonal occurrence of moderate hypoxia, while average benthic calcite saturation declines from 3.2 to 1.9. These declines are primarily driven by oxic respiration spurred by an increase in primary production and a more efficient export flux to the shelf seafloor. Model results do not include river input to the continental shelf, which is hypothesized to have further reduced oxygen and carbonate ion concentrations in the benthic environment.