8/27/2023 0 Comments Fairbanks alaska time zone![]() ![]() "These results help clarify our understanding of the fate of subducted carbon and can help improve global climate models.The length of a solar day is determined by the time that it takes for the Earth to complete a full rotation around its axis and equals 24 hours. "These results indicate less carbon is returned to the deep mantle than we previously thought," Lopez said. The scientists also found that the proportions of organic carbon and inorganic carbon recycled through arc volcanoes seemed to be influenced by characteristics of the subduction zone such as subduction speed and slab temperature. Lopez and colleagues instead found that approximately 43% to 61% of sediment-derived organic carbon is returned to the atmosphere through volcanic degassing in the central Aleutians and that approximately 6% to 9% of inorganic carbon from the slab crust is returned to the atmosphere by degassing of western Aleutian volcanoes. Previous studies concluded that minimal amounts of organic carbon in ocean floor sediments and inorganic carbon from the subducted slab crust returned to the atmosphere. Using that information, they calculated the quantity of subducted carbon released to the atmosphere through degassing of Aleutian-Alaska Arc volcanoes. The team identified the average carbon isotopic composition of the volcanic gases, as well as the isotopic composition and total amount of carbon entering the trench from the subducted slab. Inorganic carbon, organic carbon and mantle carbon all have somewhat distinct proportions of the two isotopes. The carbon 13 isotope, which has an additional neutron in its nucleus, makes up only about 1%. The carbon 12 isotope constitutes nearly 99% of Earth's carbon. ![]() Lopez and her colleagues began looking for the proportion of carbon 12 and 13 atoms in the gas coming from volcanoes. ![]() "So that means we can assume that the carbon degassing from volcanoes comes from either the mantle or the subducted slab." "From the Alaska Peninsula west, we know that the overriding crust does not have a substantial amount of carbon," Lopez said. The research focused on the Aleutian-Alaska Arc's central and western regions, which consist of oceanic crust. They tracked carbon from subduction to volcano outgassing. With that information, the researchers used chemical modeling to track what fraction of organic and inorganic carbon returns to the atmosphere from the slab subducted at the Aleutian Trench. They used data from ocean drill cores taken at four locations near the Aleutian Trench, where the Pacific Plate dives under the North American Plate. The new research drew on gas samples Lopez and others collected from 17 volcanoes during this and previous research. Organic carbon includes remains of marine plants and animals and of terrestrial plants and animals washed into the ocean. Organic carbon settles atop the sea floor-the surface of the oceanic crust slab heading toward subduction. Lopez sought to better define how much carbon is coming from the subducted slab. This makes it possible to track carbon through the subduction cycle and get a better idea of how much subducted carbon volcanoes return to the atmosphere.Ĭarbon recycled to arc volcanoes-those located above an oceanic plate subduction zone-originates from three places: the subducted oceanic plate or slab, the mantle wedge overlying the descending slab, and the overriding crust. The Aleutian-Alaska Arc, which stretches from Cook Inlet west across the Aleutian Islands, has fewer sources of carbon in its crust and subducted slab than most volcanic arcs around the world. "While we now have a fairly good idea of how much carbon is driven into Earth's interior through subduction and how much is released to the atmosphere by volcanoes, we still have a lot to learn about what happens to the carbon after it is subducted and what fraction is returned to the atmosphere," Lopez said. The 12 co-authors come from institutions in California, New Mexico, New York, Rhode Island, Washington state and Washington, D.C., as well as Italy and New Zealand. Research associate professor Taryn Lopez is the lead author on research published today in the journal Science Advances. This occurs through a process known as recycling. The finding can improve long-term projections about Earth's climate.Ī study led by a University of Alaska Fairbanks Geophysical Institute scientist has shown that volcanoes of the Aleutian-Alaska Arc return more subducted slab carbon to the atmosphere as carbon dioxide than previously thought. A new study suggests a notable amount of such subducted carbon returns to the atmosphere rather than traveling deep into Earth's mantle. ![]()
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