Jupiter’s Changing Climate

By William McLucas, Rice University, April 15, 2007

What’s happening?

Over the course of the past decade solar observers, both experts and novices, have been witnessing small changes to the visible surface of Jupiter.  These changes are represented in spots and discoloration, in terms of usual appearance, in the large banded zones that cross Jupiter in a horizontal fashion from east to west.  The bands and spots are believed to form similarly to clouds and storms on the surface of Earth.  The large bands are the result of wind driven clouds and the particles that are picked up by the wind.  The array of color patterns displayed on the planet are the result of the combination of particles, or the chemical make up of the material, caught in the clouds and their respective reflective properties.  Meanwhile the large spots found sporadically around the planet can be compared to hurricanes on Earth, but on a substantially larger scale.  These spots, or vortices, are understood to form due to the shear forces of wind jet streams across the surface of Jupiter.

There have been to changes as of recent to Jupiter’s visible surface.  Red Spot Jr., which formed from the compilation of three smaller vortices between 1997 and 2000, began to change color to a deeper red, analogous to that of its namesake The Great Red Spot, and the banded region around the equator appears darker and more turbulent than in the past.  Additionally, the banded regions north and south of the equator appear to be lighting compared to previous years.  The color of the spots and bands on the surface are theorized to coincide with temperature and wind speeds in the region.  Higher temperatures and higher wind speeds yields darker coloration while slower cooler areas render the opposite.  The higher temperatures occur in location with less cloud cover and thus are area in the atmosphere where heat can more readily escape.  While the increase in wind velocity is believed to create the accumulation of material higher in the atmosphere that reflects red light when hit by ultra violet solar rays.  The wind affect of coloration may also be the result of more turbulent environments allowing the synthesis of chemical compounds that otherwise would not occur.

Model for Change

            New research done at the University of California at Berkeley shows the potential for large-scale climate and atmospheric changes on Jupiter’s surface.  Philip Marcus, professor of physics at the University of California at Berkeley, has collected data, from as far back as 1939, on the visible changes of vortices on Jupiter and compiled this data into a model for the planet’s climate cycle.  The model calls for a 70-year cycle of the climate on Jupiter and accounts for discoloration in spots and bands according to fluid and atmospheric dynamics, namely temperature and wind.

Essentially the vortices that appear on the visible surface are characteristic of particular latitudes.  At these latitudes prevailing winds of opposite direction, moving east to west and west to east, mix creating shear forces.  The large shear forces can be attributed to the rapid rotation of the planet and thus large wind speeds.  Consequently, there horizontal lines of vortices occur on the borders of the visible bands on Jupiter’s surface where alternating wind direction occurs.  The shear forces cause swirling motion to develop and produce vortices that appear as white spots and they appear in abundance in these regions.  The lines of vortices form in sequences of one anticyclone followed by a cloud filled space then another anticyclone.  The space between the two anticyclone vortices was thought to be a buffer zone separating the storms from repelling each other, but further analysis has shown that the space is most likely a cyclone or a storm swirling in the opposite direction of the storms that sandwich it.  Thus the continual succession of anticyclone and cyclone keeps the individual vortices from repelling one another by creating a wave system, like wind circulation on Earth.

The Consequences

The formation of the Great Red spot and larger vortices results when one or more of these vortices combine to create more turbulence and magnify the strength of the storm.  This theory was established after Red Spot Jr. was created when Oval BA engulfed and at least one other vortex appearing near it on the visible surface.  Marcus’ model and observation of this super vortex synthetic process have experts preparing for substantial changes in the atmosphere and climate of Jupiter in the near future. 

The formation of larger vortex from smaller vortices swirling at the same latitudes creates a net calming effect of the climate across the planet.  The disturbance of the atmosphere and particles caught in the clouds results in very dramatic climate conditions.  Essentially this mixing of clouds and particles is the major factor for temperature variance on the planet remaining rather small.  This means the temperature at the equator and poles is relatively close.  The subtraction of many small vortices and addition of fewer large vortices would create less net disturbance of the atmosphere.  The foreseeable problem with this decrease in storm productivity is an increase in the variance of temperatures between the equator and the poles, which is forecast to result in an 18° increase in the temperature at the equator and an undetermined decrease in the polar temperatures.  Additionally, the decrease in turbulence in the atmosphere will create large gaps and clearings for heat to escape as well thus adding the temperature changes.

            Although the forces behind the changes are yet to be confirmed, the predicted changes in the atmosphere have already began to be felt on Jupiter.  The Great Red Spot has begun to change coloration from the traditional deep red to a littler salmon color and seems to be continually lighting.  The equatorial bands are becoming darker and wider then in previous years with Red Spot Jr.’s coloration darkening.  These changes in vortices patterns are attributed to the weak stability of the wave system created between cyclone and anticyclone interaction.  Slight disturbances in these systems can cause extreme changes in the circulation patterns at their respective latitudes thus producing unpredictable climatic changes in the region.  Thus dramatic changes in the atmospheric circulation and temperature patterns are going to cause considerable surface climate alteration on Jupiter.  There is, however; an upside, from our point of view from the Earth.  We will now have two templates of rapid climate changes to draw from when predicting the future of our own planet.  Scientist hope that the outcome of Jupiter’s global changes will give Earth Scientist a better idea of the potential affects of global warming and net affect of drastically changing the Earth’s environment quicker than ever before.