2000 Annual Science Report
Pennsylvania State University Reporting | JUL 1999 – JUN 2000
Evolution of Atmospheric O2, Climate, and the Terrestrial Biosphere: Approaches From Field-Oriented Geochemical Investigations - Lee R. Kump 2
During the past year, I have completed my thesis work at Penn State and submitted two of three main thesis chapters for publication.
The first of the submitted chapters is entitled “Opening Pandora’s Box: Implications of open-system modeling for interpretations of anoxia” and is in press in Paleoceanography. This study reveals that the short-term responses of marine phosphate and oxygen cycles captured by closed-system box models may be reversed on long timescales (>50,0000 years)and that the open-system and vertically stratified nature of the ocean must be captured in order to accurately assess the causes of long-term anoxia using box-models of ocean biogeochemistry.
The second submitted chapter is another study of controls on deep-sea oxygenation entitled “Ocean stagnation and Permian Anoxia” and has been submitted to Geology. We find that high-latitude warming roughly consistent with records of Late Permian climate causes reduced thermohaline overturning and deepwater anoxia in a simulated Permian ocean, a result that supports previous suggestions that anoxia may have played a role in the End-Permian extinction.
In the next few months, I will be preparing the third and final chapter of my thesis for publication. This chapter, entitled “Interpretation of a Neoproterozoic _13C gradient from the Pethei Platform (Great Slave Lake Supergroup, N.W.T.),” presents the results of a carbon isotope study of a 1.9 Ga stromatolitic reef. We find only a small vertical gradient (about -0.5â?°) between _13C of marine cements formed in shallow environments and cements in basinal carbonates inferred to have been deposited at ~1km depth. We attribute the small gradient to high marine DIC rather than weak biological pumping.
In addition to completing this third publication, I am continuing to work with Lee Kump over the summer to improve our biogeochemical general circulation model for work on Astrobiological problems.
PROJECT MEMBERS:Lee Kump
RELATED OBJECTIVES:Objective 5.0
Describe the sequences of causes and effects associated with the development of Earth's early biosphere and the global environment.
Identify the environmental limits for life by examining biological adaptations to extremes in environmental conditions.
Define climatological and geological effects upon the limits of habitable zones around the Sun and other stars to help define the frequency of habitable planets in the universe.
Determine the resilience of local and global ecosystems through their response to natural and human-induced disturbances.
Model the future habitability of Earth by examining the interactions between the biosphere and the chemistry and radiation balance of the atmosphere.