Biogeochemical modelling to explore the controls on ocean anoxia of the past
Seminar Room 1, Geographical Sciences
At this BRIDGE seminar Fanny will give a practice talk in preparation for the Gordon Research Conference on Organic Geochemistry (abstract below). Feedback and discussion very welcome.
Please note: This event is only open to University of Bristol staff and students.
The Mesozoic Oceanic anoxic events (OAEs) reflect the most dramatic changes in ocean state of the last 250 Ma. Using a data-model comparison, I provide detailed insights into the impact of temperature and ocean nutrient inventory, and associated biogeochemical responses to OAEs of the Mesozoic. The model-data reconstructions show that the spread of anoxia that these events experienced, mainly resulted from an enhancement in ocean nutrient level. Enhanced nutrient levels thus increased ocean production in the surface and oxygen consumption in the deep ocean, causing at least 40% of the ocean volume to become dysoxic/anoxic. While the spread of anoxia (and euxinia) differ between OAEs on their regional distribution as a consequence of paleogeography, the global sensitivity of oxygen to temperature and nutrient level is not paleogeography driven. I then investigate the impact of extreme ocean anoxia on the marine nitrogen circle which operated fundamentally differently during OAEs in comparison to today. In particular, the model shows shifts in community structure of phytoplankton and bacteria towards nitrogen fixers, denitrifying and sulfate reducing bacteria.