University of Leeds, UK
June 28, 2022
Marine redox dynamics across the end-Triassic mass extinction
The role of ocean deoxygenation as a cause of the end–Triassic marine mass extinction is widely debated. Here I present multi-proxy geochemical data to reconstruct the full water-column redox landscape across the shallow to deep-water marine realms of the western Tethys and eastern Panthalassa during the Triassic–Jurassic transition. Results show local dissolved oxygen decline in the near-surface ocean of low-latitude Tethys across the extinction, synchronous with the spread of deeper anoxic waters on the wider continental shelves and slopes. Further, more persistently euxinic conditions prevailed across the Triassic–Jurassic boundary in many semi-enclosed basins of the NW European epicontinental sea, coinciding precisely with the major phase of benthic faunal loss at the regional scale. Hence, the coincidence of extreme redox shifts with the extinction losses on a global scale implicates oxygen scarcity as an important factor in the crisis.
Sofía Barragán Montilla
June 23, 2022
Climate change in the North Atlantic deep ocean: lessons from the recent past
Using benthic foraminifera, this research aims to understand how deep bottom water temperatures responded to the slowdown of the Atlantic Meridional Overturning Circulation during the last deglaciation. Our geochemical multi-proxy dataset, suggests that changes in heat uptake due to significant modifications of North Atlantic circulation (similar to those predicted for the 21st century) have the potential to enhance global warming in the future.
Goethe-Universität Frankfurt am Main, Germany
June 14, 2022
The changing major ion chemistry of seawater is an important driver of long-term CO2
The cause of the observed ~1000 ppm decrease in the atmospheric concentration of CO2 through the Cenozoic remains elusive. Here, we couple a near-continuous record of the precise degree of seawater major ion chemistry change over this interval with a carbon cycle model in order to explore whether the changing chemistry of seawater is a previously underappreciated factor controlling CO2, and thus climate. Based on these results, we argue that the concentration of calcium in seawater is in itself a likely driver of the long-term carbon cycle and that the observed Cenozoic change can directly account for the bulk of the coincident CO2 decrease.
Sante Fe Institute
June 7, 2022
Exploring fundamental differences between the structures of Cambrian and modern communities
The Earth system has changed dramatically since animals first evolved, including the development of new biotic niches and the widespread oxygenation of oceans. Recently it has been hypothesized that the evolution of this system may have been driven by the relative longevity of communities with net-positive ecosystem effects. Compelling though this idea is, evidence for it in fossil data is lacking. In this talk I will show how analyses of ancient and modern food webs can elucidate the structure, function, and dynamics of communities through deep time to look for trends in such ecosystem effects. Comparisons of Cambrian and modern food webs reveal previously hypothesized changes in trophic structure across the history of animal life, including increased predation, ecological differentiation and, perhaps, greater stability. Taken in concert with our rapidly advancing understanding of environmental conditions across the Phanerozoic, this approach could be used to identify the mechanisms underlying ecological change and the regulation of the biosphere.