Tectonic plates moving beneath the Earth’s surface create volcanoes that erupt in a profusion of gases and molten rock.
But when plates move slowly over time, they also give rise to mountains, producing carbon-emitting matter that has been buried beneath the surface for millennia.
As humans pump unprecedented amounts of carbon dioxide into the atmosphere, researchers are pushing to understand how the natural carbon cycle works and how it will be affected not only by increased carbon in the atmosphere, but also by the rising temperatures and changes in weather patterns of global climate change.
For millions of years, carbon has been trapped in mountain rock. Some of it was once in the shells of tiny organisms on the seabed or in dead trees buried under the weight of the soil that, over time, consolidated into the rock. But as the Earth’s tectonic plates shift over millennia, the rock plates that once lay on the ocean floor have wrinkled, bent, or were lifted to the heights of mountains.
“When these rocks are exposed near the surface, oxygen in the air and water can react with their organic matter and release the carbon as carbon dioxide,” explained Professor Robert Hilton, a geologist at the University of Durham, UK “It’s like the Earth is breathing, this consumption of organic matter and a slow release.”
Life as we know it depends on carbon, and its movement between land, oceans and the atmosphere is called the “carbon cycle .”
Professor Hilton leads a project called ROC-CO2 that aims to quantify the contribution of organic carbon in mountain rock to this natural carbon cycle.
In previous models, mountains were thought to trap carbon from the atmosphere. Carbonic acid and water erode minerals and rocks, and carbon eventually flows into the ocean through rivers. But the release of organic carbon through erosion could reduce the amount of carbon that we assume is being removed from the atmosphere . These contributions – and knowing how they will alter as the planet warms – are important to understanding what world we will live in a century from now.
Cycle
According to Professor Susan Trumbore, Director of the Max Planck Institute for Biogeochemistry in Germany, there are many gaps in our understanding of the carbon cycle, especially in relation to the processes that take place on earth as opposed to those that occur in the oceans . “With climate change, changes in the amount of carbon dioxide available, changes in the ecosystems themselves due to changes in fauna, new diseases and new species, the ability to predict the future is poorer. We fundamentally don’t understand these processes, “he said.
During his doctorate, Professor Hilton recognized the role of mountain erosion as one of these lagoons. “I was surprised that some of these aspects are so poorly understood,” he said.
While human-linked carbon emissions and their effects are one of the main focuses of climate research – they account for around 9,400 megatons of carbon, almost 100 times more than weathering from mountains or volcanoes – the largest contributions. Small pieces are also important pieces of the puzzle and occur over longer time scales. Its effects are felt throughout the centuries and are an integral part of our climate. Anthropogenic carbon emissions, on the other hand, occur on a very small scale, causing an unprecedented rate of change in natural systems.
“We need to understand how (mountain weathering) worked in the past,” Hilton said. It’s important, he says, because the carbon cycle is so closely linked to the Earth’s climate, which in turn sets the framework for the evolution of plants and animals . And with mountains and erosion, “the earth’s surface is being cooled all the time by material moving down the slopes, putting new rocks in contact with the atmosphere and water.” .
Professor Sophie Opfergelt, a geologist at the University of Leuven in Belgium, who investigates the chemical erosion of rocks, describes mountains and erosion as one large reactor. “Mountains are ways of getting materials to the reactor. When there is uplift or erosion, more minerals and surface are exposed to the elements. “He also covers some of these materials and prevents the material from entering the reactor.
Flow
Through ROC-CO2, Hilton and his colleagues are developing techniques to measure the rate of carbon emissions or flux from mountains .
One technique, which they describe in a recent paper, measures the mountain’s carbon emissions directly by drilling a 40-cm-deep hole in the rock, and erecting an airtight chamber over it to measure the amount of carbon that is released.
“There’s carbon in the atmosphere around us and you don’t want to measure that,” Hilton said. “When we breathe out, we breathe out a lot of carbon and we’re pretty sure we don’t want to measure it. When plants breathe out, they release carbon dioxide and we don’t care. that”.
Hilton and his colleagues avoid contamination by covering the rock with the airtight chamber and repeatedly emptying it of the gases they collect for analysis. Later, in the laboratory, they have to prove that the gases are not coming from other sources.
All modern carbon contains carbon-14, an unstable form of carbon that breaks down over time . The old carbon in rocks no longer contains any of this radioactive carbon because it has already decomposed . “This is critical because otherwise people might say that they are measuring the carbon of a plant and its roots (within the rock),” said Hilton.
Another method is to look for the remnants of these reactions in the open and use them to estimate the flow. “The idea here is that when these rocks break down, other things are released that they might be able to track. So, for example, we can measure the water in a stream or river and say something about the chemical reactions that occur upstream, “said Professor Hilton.
In a 2017 paper, the authors, including Professor Hilton, measured the amount of organic carbon particles in suspended sediments from the Kosñipata River in Peru over the course of a year. They found that there was a large discrepancy between the estimated erosion in the Andes mountain range and what actually ended up in the river downstream. This raises questions about the actual carbon budget of the Amazon River basin, which is believed to be one of the major carbon sinks on the planet.
Doing research
Professor Hilton is currently investigating carbon fluxes at sites around the world, from Canada to France and from Switzerland to New Zealand.
“We recognize that we can’t measure flow everywhere,” Hilton said. The scales are ‘too large,’ but having a variety of sites, they can try to characterize flow for different environments.
“One of the reasons for doing this is to quantify global flows, but the most important thing is to say why would this flow change, what controls it, and how it responds to things like temperature changes.”
Professor Hilton hopes to finally describe how the flow has changed over the course of centuries or even millennia. “The aspiration is to be able to tell people more about why this process changes over time, in the distant geological past, or even predict what will happen in the next century.”
Researchers, including Professor Hilton, have shown that climate and increasing or decreasing rainfall and runoff affect how quickly erosion occurs. The goal is now to understand whether increased erosion could unearth even more carbon that has been locked up in rock for millennia, and further accelerate climate change. This is a question that Professor Hilton also hopes to answer.
“How could this process (flow) change to impact the natural carbon cycle?” He asked. “This affects the lifespan of carbon dioxide emissions in the atmosphere.”
Artículo original
This article was originally published in Horizon, the EU Research and Innovation Magazine
