Volcanoes: the surprise regulator of global climate

Acatenango, a Guatemalan stratovolcano, captured mid eruption. Acatenango is part of the Central American Volcanic Arc (CAVA) that runs parallel to the Pacific coast from Guatemala to Costa Rica. Image: Caitlin Wynne via Unsplash

Acatenango, a Guatemalan stratovolcano, captured mid eruption. Acatenango is part of the Central American Volcanic Arc (CAVA) that runs parallel to the Pacific coast from Guatemala to Costa Rica. Image: Caitlin Wynne via Unsplash

For a long time, scientists have understood Earth’s atmospheric temperatures to be primarily regulated by cycling carbon between continents, oceans, and the atmosphere. However, new NCRIS enabled research using GPlates software shows that, when looking over the span of millions of years, there is a surprise key player in Earth’s global ‘thermostat’: volcanoes sitting on the edge of continents and the processes that weather them.

Capturing carbon in deep time

While we are currently struggling to capture and store carbon emitted from anthropogenic sources the Earth has been absorbing carbon dioxide for millennia. One method is the absorption of carbon dioxide during the natural weathering of silicate rocks. From the tops of the Andes to the tumbling of rocks in the Cascades, these weathered rocks, full of calcium and magnesium, are flushed via rivers to the oceans where they form minerals and new rock that lock up carbon dioxide.

This process has recently captured the attention of an international team of researchers led by Dr Tom Gernon from The University of Southampton. In explaining their research topic, Dr Gernon points out that:

“...Weathering of the Earth’s surface serves as a geological thermostat… But the underlying controls have proven difficult to determine due to the complexity of the Earth system.”

Untangling a complex system

Keen to understand the role of rock weathering in greater detail, Dr Gernon and his fellow collaborators from The University of Southampton, The University of Sydney, Australian National University, The University of Ottawa and The University of Leeds tracked the complex interactions of plate tectonics and climate over 400 million years.  A central question of the study was: what rock weathering process has the most significant influence on global climate?

The team needed a powerful tool to capture the complex interrelationships between global climate and plate tectonics. The game-changing approach that helped them achieve this was the “Earth network”. An enhanced analytical system that is based on NCRIS enabled GPlates modelling software that simulates dominant Earth system interactions and how they evolved through time.

Using plate reconstructions, the team tracked mountain building, arc-continent collisions, and the clustering of continents in the tropics. Dietmar Müller, Professor of Geophysics at the University of Sydney, explains GPlates’ critical role in this process: 

“GPlates is a powerful four-dimensional information system that we have now supercharged with machine learning to understand the time lags between fluctuations in the global carbon cycle and climate change.” 

Tectonic, atmospheric and ocean chemistry changes over the past 410 Myr. GPlates-reconstructed continental distribution with landmasses shown in blue, present-day coastlines in black, and the tropics (±20° of the Equator) in green. Image: Edited from Gernon et. al., 2020

Tectonic, atmospheric and ocean chemistry changes over the past 410 Myr. GPlates-reconstructed continental distribution with landmasses shown in blue, present-day coastlines in black, and the tropics (±20° of the Equator) in green. Image: Edited from Gernon et. al., 2020

Weathering of mountain belts found to be key

A surprising result of this study, recently published in Nature Geoscience, was the correlation between weathering of volcanoes that lie along the edges of continents (known as volcanic arcs) and global climate. The team found that these ancient volcanoes were the most significant driver of weathering intensity over the past 400 million years. As a result, the study casts doubt on the concept that Earth’s long term climate stability results from the weathering of the seafloor and continental interiors. Volcanoes, it seems, are responsible for cooling the climate as well as heating it. 

The Andes are an example of a volcanic arc, a chain of volcanoes, hundreds to thousands of miles long, that forms above a subduction zone. Pictured: Región de Valparaíso, Chile. Image: Matheus Frade via Unsplash

The Andes are an example of a volcanic arc, a chain of volcanoes, hundreds to thousands of miles long, that forms above a subduction zone. Pictured: Región de Valparaíso, Chile. Image: Matheus Frade via Unsplash

Volcanoes and our future 

The delicate balance of our global climatic system is millions of years in the making. Our current climate instability results from a thermostat unbalanced by too much carbon being released into the atmosphere. NCRIS supported research is making it possible for scientists to understand the long term influences on Earth’s climate. 

The team’s findings provide critical insights into how volcanoes have and are influencing global climate. They note that artificially enhanced rock weathering, where rocks are pulverised and spread across land, could play a role in removing carbon dioxide from the atmosphere. However, Dr Gernon notes:

“This is by no means a silver bullet solution to the climate crisis — we urgently need to reduce carbon dioxide emissions in line with IPCC mitigation pathways, full stop. Our assessment of weathering feedback over long timescales may help in designing and evaluating large-scale enhanced weathering schemes, which is just one of the steps needed to counteract global climate change.”

This research has enhanced our knowledge of the complex interactions that regulate our climate. Ancient volcanoes are capturing carbon and have been for millions of years. They offer a possible climate mitigation solution in rock weathering and provide the rare earth minerals powering our green technology. Indeed, volcanoes are full of surprises and are a force to be respected and reckoned with.

 
 
 
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