|How has the Earth remained in a habitable state for life for the last 4 billion years when the sun has been getting brighter? This is a key question for Earth system scientists. In early Earth history the sun was much fainter and model studies suggest that atmospheric CO2 should have been much higher in the past to compensate. However geochemical evidence suggests that levels of CO2 may not have been so high, so we must look for other explanations to the “faint young sun paradox”. One such process is atmospheric dust.
In the contemporary Earth-system airborne dust plays an important role in climate. Winds blow dust into the atmosphere, where it absorbs solar radiation, heating the atmosphere, while cooling the surface underneath it, significantly altering climate and weather on continental scales. When deposited in the ocean the iron that it contains can stimulate the growth of marine life, which can then reduce the amount of carbon dioxide in the atmosphere, cooling the climate globally.
In the Precambrian (>700 million years ago), before the colonization of Earth’s land surface by plants and forests, much more of the land surface could have produced airborne dust, so it is very likely that wind-borne dust was far more prevalent over large parts of the surface compared to the present day. However, in the deep past of the Archean (3-4 billion years ago), when continental land mass was much smaller in area, there may have been considerably less dust in the atmosphere than now. We currently have very little understanding of how dusty the planet was in the deep past, or what role this may have played in controlling climate.
Using numerical models and geochemical proxy data the successful applicant will investigate the possible role of dust on the atmosphere, the ocean geochemistry and the climate of the Precambrian. Models include an intermediate-complexity climate model of the atmosphere for investigating how dust changes climate directly, and a so-called “Earth-System model” for investigating the effect of changing dust levels on marine chemistry, and hence on atmospheric greenhouse gas concentrations. The range of disciplines involved means that a student will gain experience in the physical, geochemical and computational approaches needed to answer not just the big questions of Earth’s past history, but also contemporary questions of direct relevance to Earth’s immediate future.