Narration: Ryan Fitzgibbons
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Between September 2019 and March
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2020, wildfires killed billions of animals and decimated more than 200,000
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square kilometers of Australian forest, an area larger than the size of Nebraska.
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Some thousands of kilometers away, in the Southern Ocean,
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massive algae blooms covering a surface larger than the area of Australia itself.
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Just how are these wildfires and ocean blooms connected?
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To untangle that, we look to the carbon cycle.
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The carbon cycle is the flow of carbon between reservoirs
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in the atmosphere, plants and animals, land and ocean.
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It's one of the key processes that keeps life sustainable on Earth.
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And at the heart of all this are land plants and aquatic phytoplankton.
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On land, most carbon is stored in forests.
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Here, plants absorb carbon dioxide from the atmosphere into their cells.
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With energy from the Sun
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plants combine carbon dioxide and water to form carbohydrates, such as sugar,
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and oxygen through photosynthesis.
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In this process, carbon dioxide is converted to carbon-based
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Carbon stored in those plants can be transferred when animals eat
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the plants, the plants die and decay,
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or, in the case of Australia, fire consumes the plants.
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And once again, carbon based cellular material becomes
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carbon dioxide that ends up in the atmosphere.
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If we look to the ocean reservoir, carbon dioxide is also absorbed
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by phytoplankton, microscopic organisms that convert carbon dioxide, water
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and sunlight into carbohydrates like sugar and oxygen through photosynthesis.
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Carbon dioxide released into the atmosphere
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eventually becomes available for aquatic photosynthesis.
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In general, any change that shifts carbon out of one reservoir
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puts more into other reservoirs.
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But photosynthesis also requires
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nutrients such as nitrogen, phosphorus and iron.
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Without the right proportions of these nutrients,
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photosynthesis doesn't happen, which can be seen in
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the iron-limited parts of the ocean, such as far offshore of Australia.
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Atmospheric aerosols released by fires, however, contain carbon
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as well as other nutrients essential for plant growth like iron.
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When these aerosols are deposited on the ocean's surface,
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these nutrients become available for photosynthesis.
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This iron from the Australian wildfires is now thought to have stimulated
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the massive southern Ocean phytoplankton blooms, blooms of such magnitude
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that they converted an almost equivalent volume of carbon dioxide
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released by the fires into carbohydrate and cellular material.
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And here is why having a
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vantage point from space is crucial.
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From satellites, we can observe how the movement of carbon changes
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when large scale events like wildfires occur.
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The connection between the Australian wildfires and Southern Ocean
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bloom could not have been made without satellites.
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NASA's Plankton, Aerosol, Cloud, and ocean Ecosystem, or PACE,
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mission, is specifically designed to better measure parts of the atmosphere
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and ocean connection with unprecedented resolution.
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PACE’s instruments will shed new light on the composition and distribution
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of these massive mixtures of tiny aerosol particles and aquatic microorganisms.
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Onboard are two polarimeters, instruments that measure specific angles
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of light reflected, which, for example, allows researchers to tease apart
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the specific type of aerosols in these kinds of massive fire events.
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PACE’s flagship sensor, the Ocean Color Instrument, or OCI, will cover vast
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swaths of the ocean, measuring concentrations of photosynthetic pigments,
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allowing researchers to decipher the different types of phytoplankton.
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With an instrument like OCI, where you're measuring
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this full spectrum of color, all the colors of the rainbow
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you can imagine, we can start teasing apart the species
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and the different functional groups and different communities that exist.
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The data from PACE will help define those communities,
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allowing for clearer connections within the reservoirs of the carbon cycle.
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These fires emitted a huge amount of carbon
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and other aerosols into the atmosphere, with some estimates suggesting volumes
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greater than Australia's annual emissions from fire and fossil fuels combined.
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Those aerosols contained essential nutrients that are thought
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to have stimulated the rapid growth of phytoplankton in the Southern Ocean.
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And these kinds of connections can have big impacts.
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It's really important to know
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where the carbon is going and where your food source is going.
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This is important for not just climate studies, but food security.
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The fires that tore through Australia are just one example
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of how Earth systems are linked in ways we're only beginning to fully understand.
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With data from PACE, we'll get a clearer picture of carbon as it links
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land use and fires, atmospheric aerosols and marine communities
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and ultimately improves the data we put into climate models.