Oliver Shorttle

How has Earth maintained climate stability for over 4 billion years?
Lead Supervisor: Oliver Shorttle, Department of Earth Sciences and Institute of Astronomy
Co-supervisors: David Hodell, Department of Earth Sciences, Sasha Turchyn, Department of Earth Sciences, Elizabeth Harper, Department of Earth Sciences


Brief summary
Earth’s history of rock weathering is written in the isotopic compositions of its oceans.  Oxygen isotopes in natural waters exchange with minerals during the low temperature weathering of rocks and during the high temperature exchange at mid-ocean ridge hydrothermal vents.  The oxygen isotope composition of seawater therefore provides a measure of how much water-rock reaction has occurred at low temperature (during weathering) and high temperature.  Seawater oxygen isotopic composition is therefore providing key information on Earth’s climate regulation mechanism.  In this project we will make novel oxygen isotope measurements of marine carbonates to reconstruct Earth’s climate regulation. 

Importance of the area of research concerned
Earth’s habitable and inhabited state is remarkable not only because of the events that led to it growing to just the right size, and endowed with just the right amount of water, carbon, and sulfur to get life started. But, because it has also managed to maintain its habitability for over 4 billion years.  This climate homeostasis, in the face of a major change in solar luminosity over that time and various cataclysms (impacts, snowball Earth events, large igneous province eruptions), suggests powerful stabilising climate feedbacks are built into the system.  Understanding these feedbacks is central to mapping the habitability of planetary systems throughout the galaxy.  In this project we will investigate how the central hypothesised mechanism for how this climate stability has been achieved on Earth, silicate weathering, has operated.  Focussing specifically on reconstructing where on the planet weathering has taken place to provide this climate stabilisation. 

What will the student do?

The student will perform oxygen triple isotope and clumped isotope analyses of brachiopod carbonate (over the Phanerozoic) and well-preserved sedimentary carbonates from the pre-Cambrian.  These measurements will be performed in the Department of Earth Science’s laser spectroscopy lab and in the Godwin laboratory.  Samples will be collected, prepared, digested, and analysed, and there is scope for individuals with interest in method development.   

Modelling of Earth’s coupled water and carbon cycles will be performed to interpret the data.   

References

  • Walker, Hays, and Kasting, 1981. A negative feedback mechanism for the long-term stabilization of Earth’s surface temperature. Journal of Geophysical Research, 86:C10:9776—9782. 
  • Pack and Herwartz, 2014. The triple oxygen isotope composition of the Earth mantle and understanding ∆17O variations in terrestrial rocks and minerals.  Earth and Planetary Science Letters, 390:138—145, doi: 10.1016/j.epsl.2014.01.017. 
  • Krissansen-Totton and Catling, 2017, Constraining climate sensitivity and continental versus seafloor weathering using an inverse geological carbon cycle model. Nature Communications, doi: 10.1038/ncomms15423. 

Requirements as to the educational background of candidates that would be suitable for the project
This project would be suitable for students with experience of Earth Sciences and Chemistry/Geochemistry and a strong interest in laboratory geochemistry. 

Applying
You can find out about applying for this project on the Leverhulme Centre for Life in the Universe widening participation PhD Studentships page.