Scientists wonder what happens to the organic and inorganic carbon that the Earth’s Pacific Plate carries with it as it sinks into the Earth’s interior along the ring of fire.
New research shows how much of this reduced carbon returns to the atmosphere instead of going deep into the Earth’s mantle.
The findings could improve long-term observations of Earth’s climate.
A study led by a scientist from the University of Alaska Fairbanks Geophysical Institute has shown that the volcanoes of the Aleutian-Alaska Arc return more reduced carbon to the atmosphere as carbon dioxide than previously thought. This is done through a process called recycling.
Research associate professor Taryn Lopez is the lead author of the study published today in the journal Advances in Science. The 12 co-authors come from institutions in California, New Mexico, New York, Rhode Island, Washington state and Washington, DC, as well as Italy and New Zealand.
“Although we now have a good idea of how much carbon is absorbed into the Earth’s atmosphere through dilution and how much it is released into the atmosphere by volcanoes, we still have a lot to learn about what happens to the carbon after it is removed and what happens in the atmosphere. This section it’s put back into space,” Lopez said.
The Aleutian-Alaska Arc, which runs from the Cook Inlet west through the Aleutian Islands, has fewer sources of carbon in its soil and a lower slab than most of the world’s mountains. This makes it possible to track emissions through the reduction process and to determine how much carbon dioxide is returned to the atmosphere.
Air recirculation at arc mountains — those above the oceanic slopes — comes from three places: the plate or slab, the inner mantle above the lower slab, and the upper crust.
Lopez wanted to better explain the carbon footprint of the reduced slab.
Organic air forms at the surface of the ocean — above the surface of the ocean. Organic matter includes the remains of plants and animals in the oceans and terrestrial plants and animals taken from the oceans.
Inorganic carbon, taken up in seawater, can sink as salt to the surface of the ocean.
The new study was based on air samples Lopez and others collected from 17 volcanoes during this period and from previous studies. They used data from ocean boreholes taken at four locations near the Aleutian Trench, where the Pacific Plate subducts beneath the North American Plate.
With this information, the researchers used chemical analysis to determine what fraction of carbon and inorganic carbon returned to the atmosphere from the slab taken from the Aleutian Trench. They tracked carbon from subduction to volcanic outgassing.
The study focused on the central and western Aleutian-Alaska Arc, which contains oceanic crust.
“From the Alaska Peninsula to the west, we know that the upper crust doesn’t have much oxygen,” Lopez said. “So that means we can assume that the release of carbon from the volcano comes from the mantle or the subducted slab.”
Lopez and his colleagues began looking at the amount of carbon 12 and 13 atoms in the air from the volcanoes. Carbon 12 isotope makes up about 99% of the Earth’s atmosphere. Carbon 13 isotope, which has an extra neutron in its nucleus, makes up about 1%. Atmospheric carbon, organic carbon and mantle carbon all have different isotope ratios.
The team determined the isotopic composition of the blast gas, as well as the isotopic composition and amount of carbon entering the tunnel from the slab. Using that information, they calculated the amount of carbon dioxide released into the atmosphere by removing the air from the Aleutian-Alaska Arc Mountains.
Previous research has shown that some of the organic carbon in the soil beneath the sea is organic carbon from the crust of the slab that returned to the atmosphere.
Lopez and his colleagues instead found that about 43% to 61% of soil-derived carbon is returned to the atmosphere through volcanic activity in the Central Aleutians and that about 6% to 9% of inorganic carbon from the slab crust is returned to the atmosphere. by removing the air from the western Aleutian Mountains.
The scientists also found that the amount of organic carbon and recycled carbon produced through arc volcanoes appears to be affected by local conditions such as ground pressure and slab temperature.
“These results show that less gas is returned to the deep mantle than we previously thought,” Lopez said. “These results help clarify our understanding of the future of subducted carbon and may help improve global climate.”
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