A new video from NASA shows how the Sahara Desert produces massive storms which send tons of dust into the atmosphere – much of which is transported across the Atlantic Ocean and deposited in the Amazon Rainforest and the Caribbean.
NASA
has measured in 3D how much dust is transported from Africa and how much
phosphorous it contains. Phosphorous is an important plant nutrient, though the
low supply of it in the Amazon means it has to come from another source.
The story continues:
That
source, it turns out, is Africa, where the phosphorus originates from an
ancient lake bed in the Bodele Depression in Chad, which itself is made up of
dead microorganisms loaded with phosphorous.
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"We know that dust is very
important in many ways. It is an essential component of the Earth system. Dust
will affect climate and, at the same time, climate change will affect
dust," Hongbin Yu, an atmospheric scientist at the
University of Maryland and the lead author of the NASA study, said in a
statement.
“To understand what those effects may be, first we
have to try to answer two basic questions. How much dust is transported? And
what is the relationship between the amount of dust transport and climate
indicators?"
NASA’s Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation
satellite, or CALIPSO, collects “curtains”
of data showing the altitude of dust layers in the atmosphere. This information
tells scientists the height the dust travels at, where it will go, and how it
will interact with the Earth’s heat balance and clouds – not only now, but also
in future climate scenarios.
The
satellite study, which collected data from 2007 through 2013, revealed the
Sahara dust storms measure 182 million tons, or the equivalent of 689,290
semi-trucks. Researchers found the storms travel 1,600 miles across the
Atlantic Ocean and drop around 27 million tons of dust on the Amazon forest,
all of which contains 22,000 tons of phosphorous.
This
is about the same amount of phosphorous that is lost annually in the Amazon
from rain and flooding, Yu said. About 43 million tons of dust travel farther
to settle over the Caribbean Sea. The finding is part of a bigger research
effort to understand the role of dust and aerosols in the environment, and on
local and global climate.
Yu’s
paper was published Feb. 24 in Geophysical Research Letters, a journal of the
American Geophysical Union. A paper published online by Yu and colleagues Jan.
8, called 'Remote Sensing of the
Environment,' provided the first multi-year satellite estimate of
overall dust transfer from the Sahara to the Amazon.
Looking
at the data year-by-year shows that that the amount of dust transferred to the
Amazon is actually highly variable. Yu said there was an 86 percent change
between the highest amount of dust transported in 2007 and the lowest in 2011.
Scientists believe this has
to do with conditions in the Sahel, the long strip of semi-arid land on the
southern border of the Sahara. After comparing the changes in dust transport to
a variety of climate factors, the one Yu and his colleagues found a correlation
to the previous year's Sahel rainfall. When Sahel rainfall increased, the next
year's dust transport was lower.
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