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Radical changes in atmospheric composition and their role in climate in the Proterozoic

Prof. Daniel Marsh (SoC), Dr. Amanda Maycock (SEE)

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During the Earth’s Proterozoic eon, around 2.5 billion to 0.8 billion years ago, atmospheric composition was very different than that of the present-day.  For example, oxygen levels were a miniscule fraction of current values, while methane and carbon dioxide levels were likely to be factors of 10 to 100 higher (Lyons at al., 2014; Kaufman and Xiao, 2003). This radically different atmospheric composition would have created a climate very different from that of today. The concentrations of oxygen in our atmosphere, combined with the influx of ultraviolet radiation from the Sun, explains the existence of a distinct ozone layer peaking at around 35 km (Chapman, 1930). Through absorption of UV radiation, the ozone layer is responsible for creating the thermally stratified layer of the atmosphere between ~10-50 km altitude known as the stratosphere. The stratosphere plays an important role in present day surface weather and climate. In earlier epochs when atmospheric oxygen levels were much lower than today, there would not exist an ozone layer, nor presumably a stratosphere as we observe today. Combined with the existence of a Nuna supercontinent, these variations in conditions would radically alter the atmosphere as we know it, including substantial differences in the large-scale structure of the atmosphere and its chemistry and weather. 

This project will use a state-of-the-art global chemistry-climate model (CESM2-WACCM) to investigate how the chemistry, radiation and large-scale atmospheric circulation of Earth would have evolved during the Proterozoic. We will focus our investigation on the period after the first great oxidation event, but before the later oxygenation event where oxygen levels similar to present day. The characteristics and variability of the large-scale atmospheric circulation will be investigated, including the stability of global weather regimes that would have impacted habitability during the Proterozoic eon. We will also investigate the role of other reactive greenhouse gases such as methane and carbon dioxide in determining atmospheric composition (e.g. water vapour production through methane oxidation) and the related influences on climate. We will further investigate the impacts of reduced solar luminosity during that time, and its potential to resolve the faint young Sun paradox. 

The student will work under the supervision of Professor Daniel Marsh and Dr. Amanda Maycock at the University of Leeds. Prof. Marsh also works at the world-leading US National Center for Atmospheric Research in Boulder, CO, and the student will have the opportunity to make an extended research visit to NCAR. This project will provide a high level of specialist scientific training in: (i) the application and development of a world-leading atmospheric chemistry-climate model; (ii) analysis and synthesis of large datasets; (iii) use of advanced High Performance Computing facilities. The student will also benefit from training organised by the Doctoral Training Programme, the National Centre for Atmospheric Science, and attendance at national/international conferences.

Related undergraduate subjects:

  • Atmospheric science
  • Chemistry
  • Computer science
  • Computing
  • Earth science
  • Environmental science
  • Geophysics
  • Oceanography
  • Physics