subject: Force of nature
posted: Fri, 16 Mar 2007 12:58:31 -0000


[This is a great article on chaos/complexity theory. Curiously, the
author avoids using that name, in fact he does not name the science
he is discussing. But he is undoubtedly referring to fractal
mathematics. - Stu]

http://www.guardian.co.uk/weather/Story/0,,2035448,00.html


Force of nature


The eastern coast of Australia is witnessing a rare and unpredictable
phenomenon: a vast maritime cyclone. But why do these whirlpools
occur? Giles Foden explores one of science's last unfathomed
mysteries

Friday March 16, 2007
The Guardian

In Edgar Allan Poe's short story A Descent into the Maelstrom, the
unnamed narrator, watching from a cliff on the Norwegian coast,
describes the appearance of a giant whirlpool: "The edge of the whirl
was represented by a broad belt of gleaming spray; but no particle of
this slipped into the mouth of the terrific funnel, whose interior,
as far as the eye could fathom it, was a smooth, shining, and jet-
black wall of water, inclined to the horizon at an angle of some
forty-five degrees, speeding dizzily round and round with a swaying
and sweltering motion, and sending forth to the winds an appalling
voice, half shriek, half roar . . ."

On Wednesday Australian oceanographers announced the discovery of a
giant cold-water eddy of the proportions of Poe's whirlpool, if not
as precipitously inclined or fast moving. Sixty miles off Sydney, the
vortex has a diameter of 200km and a depth of 1km. It is whirling
round with such force that it has lowered the sea level by almost a
metre and changed the predominant current structure in the region. It
carries more water than 250 Amazon rivers.

Australia's leading scientific body, the Commonwealth Scientific and
Industrial Research Organisation, has said the eddy is so powerful
that it has pushed further out to sea the major ocean current
popularised in the film Finding Nemo. This East Australian Current is
used by merchantmen and by sailors in the Sydney-Hobart race down the
east coast of Australia, but so far the giant eddy has not affected
shipping.

It is unlikely to do so, but scientists will be hard pushed to say
exactly what will happen, because behind eddies and vortices lies the
phenomenon of turbulence - one of the last great scientific problems
of the modern age. The great quantum theorist Werner Heisenberg said:
"I will have two questions for God on my death bed: why relativity,
and why turbulence? I really think he may have an answer to the first
question."

Ocean eddies are found all over the world. They are a normal
occurrence in nature. They happen when different flows meet. Along
with their close cousins atmospheric eddies (eddies in air), and the
combined effects of sun and wind, they are among the most important
processes affecting weather. Eddies perform some of the work of
transferring energy from one part of a weather system to another.

Regulated mainly by the flux and reflux of the sea, eddies obey some
mathematical rules, but not all. Only partly predictable, they are a
consequence of turbulent disorder but also display structure, rhythm
and other characteristics associated with order.

Eddies never repeat themselves exactly, so statistics or analogues of
their behaviour cannot solve the "problem" entirely. The Americans
made that mistake when trying to forecast weather for the invasion of
D-Day by averaging 40 years of Channel weather data. They had to be
rescued by British and Norwegian forecasters using pattern-based
approaches.

While they cannot be described as a freak of nature, eddies as large
as that discovered off Sydney can play a significant part in
unexpected climate events, particularly "El Niño"-style anomalies,
from torrential rains in Peru to droughts in Kansas.

Ocean eddies are caused by the mixing of water from contrasting
sources, with different temperatures and/or flow rates. The resulting
clash, or "turbulence", can have unexpected results. This
unexpectedness is linked to the wider climate-change jigsaw insofar
as higher emissions of carbon dioxide and methane cause instability,
which in turn causes even more unpredictable mixing.

Ratchet up all these variables and the maths involved becomes mind-
boggling. One of the things scientists have struggled to understand
(and have been arguing about since the 1920s) is the relationship
between uniform and non-uniform motion in eddies, which is a key
factor in their predictability.

The biggest trick pulled by turbulent flows like the great Australian
eddy is to alter according to the scale on which they are observed:
look at them from one point of view or across a particular time slot
and you will see as calm what appears rough when looked at from
elsewhere or another time. That is why, if you sail across one, the
water will seem placid; the movement is on too big a scale to affect
even the largest boats.

Probably the Sydney eddy will soon dissipate its energy. Giant eddies
usually last about a week, but some can keep swirling for up to a
month. They do not "cease", but transfer energy by pulling smaller
eddies into their vortex.

Energy cascades up and down something like a vortical stairway, from
molecular movement through eddies in water and air to the edge of the
atmosphere, where the mystery of turbulence opens again into the
flows of interplanetary space. Scientists have found whirlpools in
the wakes of stars.

Looking at an eddy in motion - something only really possible since
the advent of satellite technology - one is really studying the
exchange of information across different scales. That is why the
science associated with eddies is closely followed by those concerned
with the vast financial flows of global stock markets. The new book
by the former chairman of the Federal Reserve, Alan Greenspan, is not
called The Age of Turbulence for nothing.

Other mathematicians model the "eddy motion" of information passing
across the internet or through a hive of ants or the human nervous
system. These areas and other complex systems are all subject to
something like what is happening off the Australian coast, and
turbulence is the key.

It is no wonder scientists have been puzzled by it - because
turbulence itself is a wonder. Artists from Dante and Da Vinci to
Damien Hirst have been entranced by the possibilities of the spiral.
Turner wrote of and painted "vapoury turbulence", while Joseph Conrad
described novel-writing as the "snatching of vanishing phrases of
turbulence". In Mallarmé's modernist poem A Throw of the Dice, a
Conradian sea captain has to decide, with his ship pitched on the
edge of a whirlpool, whether it is still worth throwing a dice.

The characteristic shape that turbulence produces is the "whorl" -
like the spiral on your fingertip. Look closely and you will see that
shape everywhere, from conch shells to pine cones to that vast eddy
edging towards the Sydney opera house - and who knows where else. It
is in the nature of turbulence to surprise.

---

Turbulence, Giles Foden's novel about the D-Day weather forecast, is
published by Faber next year

---
* Origin: [green life] revolution through evolution -
http://www.cyberdelix.net/green/

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