Elements Special Issue: When the Carbon Cycle Went Awry

In a special collection of papers in Elements, DCO scientists highlight catastrophic disruptions to the deep carbon cycle during Earth’s history. The research underscores the magnitude of current human carbon dioxide emissions and puts into historical perspective its potential impact on Earth’s climate.

Elements coverFor 10 years, DCO scientists have advanced our understanding of the amounts of carbon within different parts of Earth, and the movement between different reservoirs, both today and through deep time. Much of this work has refined our estimates of the “steady-state” carbon cycle, but Earth wasn’t always so steady. Brief, violent periods in Earth’s history often coincided with serious disturbances to the carbon cycle, which played an outsized role on the evolution of the planet and its life forms.

In a special, open-access issue of Elements, DCO collaborators investigate major, rapid shifts in the carbon cycle, including their impact on Earth and contribution to mass extinctions. DCO Reservoirs and Fluxes Community members Celina Suarez (University of Arkansas, USA), Marie Edmonds (University of Cambridge, UK), and Adrian Jones (University College, London, UK) edited the collection.

The special issue grew out of the September 2018 meeting on catastrophic perturbations to Earth’s deep carbon cycle in Reykjavik, Iceland. The collection features research on “carbon catastrophes” such as giant meteor impacts and less than million-year volcanic eruptions that sent excessive amounts of carbon dioxide into the atmosphere in a geologically short period of time and altered the planet’s climate. New papers also cover the factors causing shifts between icehouse and greenhouse periods, and the mass extinction events associated with disruptions to the global carbon cycle. One paper also details the planetary collisions that gave Earth its original carbon supply. 

Carbon box model
Carbon cycles between surface and deep reservoirs on time scales that reach up to millions of years, with the great majority of carbon residing in the lower mantle. Credit: Celina Suarez, Marie Edmonds, and Adrian Jones, adapted from Lee et al.

The focus on catastrophic events from Earth’s past also brought into focus the extent of current greenhouse gas emissions caused by burning fossil fuels. “Anthropogenic contributions to the atmosphere far, far outweigh the natural carbon input into the atmosphere,” said Suarez. “When we went back into the geologic past, we saw that the amount of carbon being pumped into the atmosphere is at a similar magnitude – or more – than these catastrophic carbon perturbations.” The only major past disruptions that put more carbon into the atmosphere than at present were bolide impacts, such as the giant meteor that caused the Cretaceous–Paleogene extinction event, about 66 million years ago. 

By synthesizing and applying the advances that DCO scientists have made in characterizing the steady-state carbon cycle, scientists can continue to probe past events that perturbed carbon cycling and quantify the changes with greater resolution. For example, scientists can use variations in carbon isotopes across the mantle, the movement of the supercontinents, and how rates of carbon fluxes have changed, all throughout deep time, to investigate ancient, catastrophic events.  

“All of these questions couldn’t really be asked before DCO,” said Suarez. “Now that we have this knowledge that DCO scientists have determined in the last 10 years, it allows us to ask questions and opens the door to more opportunities to better understand the entire deep carbon cycle.”

biogeochemical c cycle
Perturbations to the biogeochemical carbon cycle frequently coincided with mass extinctions. Credit: Mark Schobben

Papers in the Elements special issue, Catastrophic Perturbations to Earth’s Deep Carbon Cycle include:

Earth Catastrophes and their Impact on the Carbon Cycle
Celina A. Suarez, Marie Edmonds, Adrian P. Jones 

On the Origin(s) and Evolution of Earth’s Carbon 
Sami Mikhail, Evelyn Füri 

The Influence of Large Bolide Impacts on Earth’s Carbon Cycle
Balz S. Kamber, Joseph A. Petrus 

Deep Carbon and the Life Cycle of Large Igneous Provinces 
Benjamin A. Black, Sally A. Gibson 

Earth’s Outgassing and Climatic Transitions: The Slow Burn Towards Environmental “Catastrophes”?
N. Ryan McKenzie, Hehe Jiang 

Interpreting the Carbon Isotope Record of Mass Extinctions
Martin Schobben, Bas van de Schootbrugge, Paul B. Wignall 

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