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NASA | Earth Science Week: Keeping Up With Carbon
Poziom:
Temat: Środowisko
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Carbon is the basic building block of life and these unique atoms are found
everywhere on Earth. Carbon makes up the Earth's plants and animals,
and Carbon is also stored in the ocean, in the atmosphere, and the crust of the planet. A Carbon atom
could spend millions of years moving through the Earth in a complex cycle. Understanding
the Carbon cycle, and how it is changing, is key to understanding Earth's changing climate.
On land, plants remove carbon from the atmosphere through photosynthesis.
Animals eat plants and either breath out the Carbon or it moves up the food chain.
When plants and animals die and decay,
they transfer carbon back to the soil. Moving offshore,
the ocean holds huge amounts of Carbon, about 50 times the amount we find in the
atmosphere. "The ocean's sometimes called a 'Carbon sink,' meaning that is absorbs or takes up
Carbon from the atmosphere. It takes up Carbon through physical and biological
processes.
At the ocean's surface, CO2 from the atmosphere dissolves into the water.
Tiny marine plants called phytoplankton use this CO2 for
photosynthesis. Phytoplankton are the base of the marine food web.
After animals eat the plants, they breathe out the carbon or pass it up the food chain.
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Sometimes phytoplankon die
decompose, and are recycling in the surface waters. Phytoplankton can
also sink to the ocean floor, carrying Carbon as they descend.
Over long timescales, this process has made the ocean floor the largest reservoir
of Carbon on the planet. Most of the ocean's nutrients are
in cold deep water. In a process called upwelling, currents bring nutrients and
Carbon up to the surface. Carbon can then be released as a gas back into the atmosphere,
continuing the Carbon cycle. By cycling huge amounts of
Carbon, the ocean helps regulate climate. "So when you think of climate, you don't
often think of the ocean. Climate you think of, is it going to be hotter this year, is it going to be colder
this year. But the oceans are actually a great regulator, a controller
of the Earth's climate, and they even are controlling how much Carbon is in the atmosphere.
which can slow down how quickly climate change is occurring.
At the most basic level, the balance between incoming sunlight and
outgoing heat determines the Earth's climate. Greenhouse gases
act like a blanket, and trap heat in the atmosphere. Carbon dioxide is
a greenhouse gas. In the past two centuries humans
have increased atmospheric CO2 by more than 30%, by burning
fossil fuels and cutting down forests. The Earth has not experienced CO2
levels this high for the past sevral million years. Researchers
are learning that future climate change will depend on Carbon levels in the land,
in the atmosphere, and in the sea, and how these levels respond to human disturbance.
About 1/3 of all human generated Carbon emissions has dissolved in the ocean.
More than 80% of Earth's added heat is now stored in the ocean.
"In the future, as the planet gets warmer, the water's going to warm up.
And warm water can hold less Carbon than cold water. The other thing is
on a warmer planet, some of the currents are going to slow down and so we might not be forming
as much of this cold deep water. So we won't be able to transport Carbon into the deep
sea. So on the whole, the ocean's going to become less effective at removing
Carbon from the atmosphere." Throughout most of Earth's ocean,
the warmer water, weaker circulation, and new temperature gradients
that result from climate change will impact marine life and ecosystems.
These changes effect the ocean's ability to store Carbon. Increased CO2 in the atmosphere impacts
marine life in other ways. "As the ocean absorbs more CO2 it becomes more
acidic. And this can be a threat to some of the organisms that live inside the ocean."
As Earth's climate continues to change, how will researchers monitor something
as big as the ocean, and something as complex as the Carbon cycle?
NASA Earth observing satellites give scientists the "big
picture" view of our home planet. Varied satellites help researchers detect
changes in ocean climate and ecology over time, providing vital insight
into the health of our home planet.
