The Iron Experiments
Richard Barber's Team Goes to the End of the Earth to See
if Dust Once Played a Role in Climate Change
By Monte Basgall
A five-person contingent from the
Nicholas School cruised to what is literally Earth’s end in
early 2000 as part of a three-ship expedition to ferret out
whether airborne dust may have once changed Earth’s climate.
A resulting 48-author paper published
in the April 16, 2004 issue of the research journal Science
suggests that iron in ancient dust may have induced ocean
plants to remove massive amounts of carbon dioxide from the
air as our planet moved into past ice ages. Still unanswered
is a controversial second question: whether a proposed massive
effort to salt the oceans with tankerfuls of iron powder could
allay contemporary threats of global warming?
Doing this kind of science was especially
difficult because the locale was the Southern Ocean, a cold,
stormy cloak of uncertainty that wraps around the south polar
continent of Antarctica, according to expedition member Richard
Barber.
“There are a lot of unknowns in
the Southern Ocean,” says Barber, the Harvey W. Smith Professor
of Biological Oceanography and chair of the Nicholas School’s
Division of Coastal Systems Science and Policy. “It is by
far the least studied ocean because it is so difficult to
get to and so hard to work there. There are a lot of places
in the North Atlantic where there is a short period in the
winter when you can’t do work. With the Southern Ocean there
is only a short period in the summer when you can do work.”
Covering a full 20 percent of Earth’s
surface, the Southern Ocean not only is inhospitable, its
boundaries are hard to define. They are not separated from
other oceans by intervening land but by “hydrodynamic barriers.”
These barriers are wet boundaries where cold southern polar
waters and warmer waters pushing down from the north meet
in fronts. Along them colder flows knuckle down beneath the
warmer ones. Meanwhile, winds whipping perpetually around
Antarctica drive a continuous surface current and also stoke
monster waves in stormy seasons.
Then there are the annual freeze-ups
that each winter turn an area of the Southern Ocean —twice
as large as the continental United States including Alaska—
into seasonal sea ice. Since this ice forms from the fresh
component of seawater, what is left is expelled into a dense,
very cold and salty layer that sinks to help drive the rest
of the planet’s ocean current system. Each spring, fresh water
from all that melting ice then forms a layer near the surface
that becomes a favorable environment for tiny floating marine
plants called phytoplankton.
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