Earth’s climate and oxygenation history – Dahl Group

Atmospheric oxygen (O2) is essential for all humans and animals, and exclusively a product of life. Yet, Earth was born anoxic and evolved to its current oxygenated state. The colonization of land by plants likely doubled atmospheric O2 levels and fueled more energy to the aerobic biosphere, while cooling our planet by removing 90% of atmospheric CO2. Abrupt climatic events in the past have changed global conditions, for example by cooling the Earth. We work to understand the dynamics of global events using novel geochemical tools applied to the geological archives. We integrate this with Earth system models to understand how O2 and CO2 are regulated. 

Land plants doubled O2 levels on Earth and kickstarted animal evolution.
Dahl TW, Hammarlund EH, Anbar AD, Bond DPG, Gill BC, Gordon GW, Knoll AH, Nielsen AT, Schovsbo NH, Canfield DE 2010. A Devonian rise of atmospheric oxygen correlated to the radiations of terrestrial plants and predatory fish. Proceedings of the National Academy of Sciences 107, 17911-17915 (2010). 

Global-scale dynamics between O2 and nutrients during the Cambrian explosion of life
Dahl TW, Connelly JN, Li D, Kouchinsky A, Gill BC, Porter S, Maloof AC, Bizzarro M. Atmosphere-ocean oxygen and productivity dynamics during early animal radiations. Proceedings of the National Academy of Sciences, 116 (39) 19352–19361 (2019). 

Calibration of global proxies to constrain redox conditions on the early Earth
Dahl TW, Chappaz A, Lyons T, Fitts J, Molybdenum reduction in a sulfidic lake: Evidence from X-Ray Absorption Fine-Structure Spectroscopy and implications for the Mo paleoproxy. Geochimica et Cosmochimica Acta 103: 213–231 (2013).