Report
Teaser, summary, work performed and final results
Periodic Reporting for period 2 - OXYGEN (Quantifying the evolution of Earth\'s atmosphere with novel isotope systems and modelling)
Teaser
Atmospheric oxygen is fundamental to life as we know it, but its concentration has changed dramatically over Earth’s 4.5 billion year history. An amazing qualitative story has emerged, in which Earth’s atmosphere was devoid of free oxygen for the first 2 billion years of...
Summary
Atmospheric oxygen is fundamental to life as we know it, but its concentration has changed dramatically over Earth’s 4.5 billion year history. An amazing qualitative story has emerged, in which Earth’s atmosphere was devoid of free oxygen for the first 2 billion years of planetary history, with two significant increases in concentration at ~2.4 and ~0.55 billion years ago. Both oxygenation events were accompanied by extreme climatic effects – the “snowball earth†episodes – and paved the way for massive reorganization of biogeochemical cycles such as the Cambrian radiation of macroscopic life. Despite these profound influences on the Earth system, we currently lack fundamental quantitative constraints on Earth’s atmospheric evolution. I am poised to add substantial quantitative rigor to Earth’s atmospheric history, by constraining the concentrations of important gases (e.g., O2, O3, CO2, CH4, organic haze) in ancient atmospheres to unprecedented accuracy. I will accomplish this via an innovative interdisciplinary program focused on the unusual mass-independent isotope fractionations observed in sedimentary rocks containing sulfur and oxygen. These signals are direct remnants of ancient atmospheric chemistry, and contain far more information than can currently be interpreted. This project combines novel experimental and methodological approaches with state-of-the-art numerical modelling to significantly advance our ability to decipher the isotope records. Novel analytical methodologies that are cheaper and less dangerous than existing, will vastly increase the global geochemical database. The experimental results and data will provide ground-truth for next-generation atmospheric models that will constrain atmospheric composition and its feedbacks with the Earth-biosphere-climate system during key points in our planetary history.
Work performed
At the halfway point, we have:
Developed novel methodology (IE-CRDS) for measuring triple oxygen isotopes in nitrates, and published in RCMS
Obtained geologic samples from Russia, USA, Chile, and the UK.
Analyzed the worlds oldest salt deposits, and published our results in Science
Created a quadruple sulfur isotope model and published our results in PNAS and Astrobiology.
come close to completing the worlds second Curie Point Pyrolysis line for multiple sulfur isotopes.
Final results
Our analytical challenges were the highest risk component of the project, so it is excellent news that these beyond the state of the art components both seem to work.
Ongoing work that should lead to publications before the end of the project:
We are developing a triple oxygen isotope photochemical model, and reinvestigating classic results in oxygen/ozone chemistry in low O2 cases.
We are developing key numerical techniques (MCUP-SA and Bayesian Inverse modeling) for 1-D photochemical modelling which will enable us to quantify and reduce uncertainties in photochemical predictions.
We will produce interesting papers on both sulfur and oxygen MIF in key intervals in Earth History, with key constraints for the evolution of atmospheric chemistry
Website & more info
More info: https://mif.wp.st-andrews.ac.uk/.