Researcher Predicts Global Climate Change on Jupiter as Giant Planet's Spots Disappear

http://www.berkeley.edu/news/media/r..._jupiter.shtml

Researcher predicts global climate change on Jupiter as giant planet's spots
disappear

By Sarah Yang
UC Berkeley
21 April 2004

BERKELEY - If a University of California, Berkeley, physicist's vision of
Jupiter is correct, the giant planet will be in for a major global
temperature shift over the next decade as most of its large vortices
disappear.

But fans of the Great Red Spot can rest easy. The most famous of Jupiter's
vortices - which are often compared to Earth's hurricanes - will stay put,
largely because of its location near the planet's equator, says Philip
Marcus, a professor at UC Berkeley's Department of Mechanical Engineering.

Using whirlpools and eddies for comparison, Marcus bases his forecast on
principals learned in junior-level fluid dynamics and on the observation
that many of Jupiter's vortices are literally vanishing into thin air.

"I predict that due to the loss of these atmospheric whirlpools, the average
temperature on Jupiter will change by as much as 10 degrees Celsius, getting
warmer near the equator and cooler at the poles," says Marcus. "This global
shift in temperature will cause the jet streams to become unstable and
thereby spawn new vortices. It's an event that even backyard astronomers
will be able to witness."

According to Marcus, the imminent changes signal the end of Jupiter's
current 70-year climate cycle. His surprising predictions are published in
the April 22 issue of the journal Nature.

Jupiter's stormy atmosphere has a dozen or so jet streams that travel in
alternating directions of east and west, and that can clock speeds greater
than 330 miles per hour. As on Earth, vortices on Jupiter that rotate
clockwise in the northern hemisphere are considered anticyclones, while
those that spin counterclockwise are cyclones. The opposite is true in the
southern hemisphere, where clockwise vortices are cyclones and
counterclockwise spinners are anticyclones.

The Great Red Spot, located in the southern hemisphere, holds title as
Jupiter's largest anticyclone; spanning 12,500 miles wide, it is large
enough to swallow Earth two to three times over.

Unlike the cyclonic storms on Jupiter, Earth's hurricanes and storms are
associated with low-pressure systems and dissipate after days or weeks. The
Great Red Spot, in comparison, is a high-pressure system that has been
stable for more than 300 years, and shows no signs of slowing down.

About 20 years ago, Marcus developed a computer model showing how the Great
Red Spot emerged out of and endured in the chaotic turbulence of Jupiter's
atmosphere. His efforts to explain the dynamics governing it and other
vortices on Jupiter led to his current projection of the planet's impending
climate change.

He says the current 70-year cycle began with the formation of three distinct
anticyclones - the White Ovals - that developed south of the Great Red Spot
in 1939. "The birth of the White Ovals was seen through telescopes on
Earth," he says. "I believe we're in for a similar treat within the next 10
years."

Marcus says the first stage of the climate cycle involves the formation of
vortex streets which straddle the westward jet streams. Anticyclones form on
one side of the street, while cyclones form on the other side, with no two
vortices rotating in the same direction directly adjacent to each other.

Most of the vortices slowly decay with turbulence. By stage two of the
cycle, some vortices become weak enough to get trapped in the occasional
troughs, or Rossby waves, that form in the jet stream. Multiple vortices can
get caught in the same trough. When they do, they travel bunched together,
and turbulence can easily make them merge. When the vortices are weak,
trapping and merging continues until only one pair is left on each vortex
street.

The noted disappearance of two White Ovals, one in 1997 or 1998 and a second
in 2000, exemplified the merging of the vortices in stage two, and as such,
signaled the "beginning of the end" of Jupiter's current climate cycle, says
Marcus.

Why would the merger of vortices affect global temperature? Marcus says the
relatively uniform temperature of Jupiter - where the temperatures at the
poles are nearly the same as they are at the equator - is due to the chaotic
mixing of heat and airflow from the vortices.

"If you knock out a whole row of vortices, you stop all the mixing of heat
at that latitude," says Marcus. "This creates a big wall and prevents the
transport of heat from the equator to the poles."

Once enough vortices are gone, the planet's atmosphere will warm at the
equator and cool at the poles by as much as 10 degrees Celsius in each
region, which is stage three of the climate cycle.

This temperature change destabilizes the jet streams, which will react by
becoming wavy. The waves steepen and break up, like they do at the beach,
but they then roll up into new large vortices in the cycle's fourth stage.
In the fifth and final stage of the climate cycle, the new vortices decrease
in size, and they settle into the vortex streets to begin a new cycle.

The weakening of the vortices is due to turbulence and happens gradually
over time. It takes about half a century for newly formed vortices to
gradually shrink down enough to be caught up in a jet stream trough, says
Marcus.

Fortunately, the Great Red Spot's proximity to the equator saves it from
destruction. Unlike Jupiter's other vortices, the Great Red Spot survives by
"eating" its neighboring anticyclones, says Marcus.

Marcus notes that his theory of Jupiter's climate cycle relies on the
existence of a roughly equal number of cyclones and anticyclones on the
planet.

Since the telltale signs of vortices are the clouds they create, it was easy
to miss the presence of long-lived cyclones, says Marcus. He explains that
unlike an anticyclone's distinct spot, cyclones create patterns of
filamentary clouds that are less clearly defined.

"On the face of it, it is easy to think that Jupiter is dominated by
anticyclones because their spinning clouds show up clearly as bull's-eyes,"
says Marcus.

In the paper in Nature, Marcus presents a computer simulation showing that
the warm center and cooler perimeter of a cyclone creates the appearance of
the filamentary clouds. In contrast, anticyclones have cold centers and
warmer perimeters. Ice crystals that form in the anticyclone's center swell
up and move to the sides where they melt, creating a darker swirl
surrounding a lighter colored center.

Marcus approaches the study of planetary atmospheres from the untraditional
viewpoint of a fluid dynamicist. "I'm basing my predictions on the
relatively simple laws of vortex dynamics instead of using voluminous
amounts of data or complex atmospheric models," says Marcus.

Marcus says the lesson of Jupiter's climate could be that small disturbances
can cause global changes. However, he cautions against applying the same
model to Earth's climate, which is influenced by many different factors,
both natural and manmade.

"Still, it's important to have different 'labs' for climate," says Marcus.
"Studying other worlds helps us better understand our own, even if they are
not directly analogous."

Marcus's research is supported by grants from the NASA Origins Program, the
National Science Foundation Astronomy and Plasma Physics Programs and the
Los Alamos National Laboratory.

Ron wrote:
http://www.berkeley.edu/news/media/r..._jupiter.shtml

Researcher predicts global climate change on Jupiter as giant
planet's spots disappear

It's Bush's fault. ;^)

On a sunny day (Wed, 21 Apr 2004 22:12:56 GMT) it happened "Bob Harrington"
wrote in IlChc.2$0u6.1170@attbi_s03:

Ron wrote:
http://www.berkeley.edu/news/media/r..._jupiter.shtml

Researcher predicts global climate change on Jupiter as giant
planet's spots disappear

It's Bush's fault. ;^)
Of cause.