CIFAR-ESEP Postdoctoral Fellowships

The Canadian Institute for Advanced Research, Earth System Evolution Program (ESEP) is seeking to fill three postdoctoral associate positions. Successful applicants will conduct collaborative research under the sponsorship of CIFAR and two or more ESEP Scholars/Fellows on any topic of mutual interest within the Earth system sciences.

Possible areas of research include (with sponsors identified)

Magmatic uplift and climate-erosion coupling in active magmatic arcs
(Peter Reiners, University of Arizona Jean Braun, Universite Joseph Fourier - Grenoble)

Late Cretaceous to present global plate boundary reconstruction
(David Rowley, University of Chicago Alessandro Forte, Universite du Quebec a Montreal (GEOT0 P) Jerry Mitrovica, Harvard University)

Quantitative evaluation of ocean anoxia and euxinia in Earth history
(Lee Kump, Penn State University; Dan Schrag, Harvard University)

Water-plant interactions and the Miocene rise ofC4 grasslands in North America

(Kate Freeman, Penn State University Sharon Cowling, University of Toronto)

To apply, please forward a cover letter, an updated CV and the names of three potential references to Patricia Wickham (esep.cifar.postdocs201O@gmail.com) by March 15, 2010. The cover letter should identify the specific research area(s) of interest in the above list, or provide a short (one page) proposal highlighting an alternative research direction. In either case, applicants are welcome to contact relevant members of the Earth Systems Evolution Program in advance of submission.

•    Magmatic uplift and climate-erosion coupling in active magmatic arcs
(Peter Reiners, University of Arizona; Jean Braun, Université Joseph Fourier - Grenoble)

In many tectonic settings patterns of rock and surface uplift may be controlled by magmatic intrusions, leading to dynamic coupling of magmatic and surficial processes. Surface uplift caused by plutonic intrusion, for example, may increase erosion through increased gradient and orographic precipitation, which may focus further rock uplift and intrusion, leading to a positive feedback. The surface uplift may be created by the additional mass/volume of the intrusion, thermal expansion and/or by the dynamic topography associated with the pluton rise in the lithosphere, depending on the size of the intrusion, its viscosity and the various stages of its ascent/emplacement. We seek to understand the relationships between magmatic intrusion, surface uplift, and erosion through a combination of thermochronologic, petrologic, and geomorphic studies in plutons and country rocks in the active Cascades magmatic arc and other settings, and through numerical modeling using state-of-the-art dynamical codes simulating these processes. This ideal candidate would have a strong background in geology and the computational skills required to perform large-scale calculations using an existing three-dimensional creeping flow model.

•    Late Cretaceous to present global plate boundary reconstruction
(David Rowley, University of Chicago; Alessandro Forte, Université du Québec à Montréal (GEOTOP); Jerry Mitrovica, Harvard University)

We seek support for a CIFAR-ESEP post-doc to work collaboratively with David Rowley, Alex Forte, Jerry Mitrovica to create a new generation of high resolution global plate boundary maps as a function of time. Plate boundary maps are a critical input for a number of different aspects of ESEP-related research, including providing necessary boundary conditions for analysis of backward advection calculations (Moucha et al. 2008, 2009), plate deceleration calculations (Forte et al. 2009), and estimates of variations in plate properties as a function of time-crustal production rate (Rowley 2002), spreading rate variability (Rowley, in prep), subduction length and ridge length variability, etc. A first generation set of plate boundary maps was compiled by Rowley in about 2005, together with associated plate rotation files and estimated instantaneous rotations of plates. These boundary files have been used in existing published geodynamic simulations (Moucha et al. 2008, 2009; Forte, 2009), but need to be updated to include more recent plate reconstruction parameters and more robust estimates of the uncertainties in the reconstructions, and associated rotation parameters that underlie the integrated analysis. We therefore seek support for a postdoc to work most closely with Rowley on the updating of these maps and their publication. This post-doc will also work with Forte, Mitrovica, and potentially also Braun and Beaumont, who also have interests in large-scale geodynamic simulations for which such plate boundary maps are a necessary foundation. The existing suite of plate boundary maps only extend back to 55 Ma and are currently spaced every 5 Ma, We would seek to at least double the number of intervals and work toward extending the maps back to 83 Ma, the end of the long Cretaceous magnetic normal superchron. Recently resurrected interactive 3D plate reconstruction software-paleomapping tool (pmt)-will allow for more rapid assessment of global reconstruction parameters, particularly of the more poorly constrained parts of the global plate boundary system (i.e. circum-Pacific and Tethyan arc systems) than was possible in the previous version. Efforts will be extended towards creating paleo-plate age grids, recognizing the difficulties inherent in extrapolating plate histories beyond the observed record (Rowley, 2009). The reconstructed paleo-age distribution in oceanic basins provides a crucial constraint on the thermal evolution of upper horizontal boundary layer (i.e. lithosphere) in current efforts to carry out time-reversed mantle convection simulations (e.g. Moucha et al. 2009). The maps will also be of interest to a number of others in ESEP (Derry, Schrag, Kump, Turchyn to name a few) who are interested in geochemical cycles and potential feedbacks associated with both hydrothermal systems along ridges and erupted and erosional fluxes associated with plate convergence.

•    Quantitative evaluation of ocean anoxia and euxinia in Earth history
(Lee Kump, Penn State University; Dan Schrag, Harvard University)

Several lines of evidence and argument support the notion that after the "rise" of atmospheric oxygen, the Proterozoic ocean became highly reducing, with high levels of hydrogen sulfide (euxinia). While this oceanic state is compatible with box models, the conditions under which it might exist and persist has not been fully explored using more sophisticated ocean/atmosphere general circulation models. The postdoc selected for this project will work with Dan Schrag (Harvard) and Lee Kump (Penn State), together with their colleagues and graduate students, to thoroughly investigate the nature of the Proterozoic ocean, the persistence of euxinia in time and space, and its implications for the evolution of life and environment during this critical interval of Earth history. Although numerical modeling will be the primary tool, opportunities exist for field work and geochemical/isotopic analysis. Candidates with backgrounds in oceanography and quantitative analysis with an interest in deep time are especially encouraged to apply.

•    Water-plant interactions and the Miocene rise of C4 grasslands in North America
(Kate Freeman, Penn State University; Sharon Cowling, University of Toronto)

This project focuses on interactions between hydrology and vegetation during the Miocene transition from forested landscapes to open grasslands in the North American Great Plains. Feedbacks between climate and vegetation potentially centered on changing moisture budgets across the landscape with the shift from canopied to open three-dimensional structures in plant communities. Constraining timing and drivers of the transition from closed (C3 forests) to open (C4 grasslands) landscapes demands both proxies that can separate vegetation and climatic changes and better theoretical understanding of water-plant and climate-landscape feedbacks. Shifts from C3 forest to C3 grassland, C3 savannah, or C4 grassland affect leaf physical properties and gas exchange regulation, impacting both water and carbon cycling at the plant level, with larger spatial-scale consequences for albedo, evapotranspiration, water budgets and geomorphic processes.

We propose to advance understanding of climate-ecosystem structure relationships using models combined with molecular and isotope data. We will test the quantitative resolution of biomarker and compound-specific hydrogen and carbon isotope signatures as independent proxies for vegetation and climate using modern plants, sediments and soils from a range of C3 and C4 landscapes. We will also apply proxies to sediment archives in North America to validate model findings and directly test linkages between vegetation and climate in the late Miocene. Theoretical models will be developed to strengthen understanding of ecophysiological response of the biosphere to abiotic stresses over various spatio-temporal scales. Initially, we will use statistical models and a meta-data approach (drawing from published 13C/12C and D/H data for modern leaves), with the objective of revealing isotopic signatures encoded by ecosystem form and function. Drawing from both the meta-analysis and new molecular and isotopic data, our larger objective is to derive a mechanistic, process-based model. This dynamic model ultimately is intended to provide a solid framework for predicting potential future responses to changing environments and serve as an essential tool for understanding paleo-ecosystem processes across Miocene landscapes.