September 24, 2012
Research Shows Deep Ocean Currents Influenced By Atmospheric Winds
Brett Smith for redOrbit.com - Your Universe Online
Atmospheric researchers at the University of Utah have uncovered a Rube Goldberg-like mechanism that begins in the polar stratosphere and drives global weather patterns through a chain of interactions, according to a new report."It is not new that the stratosphere impacts the troposphere," said University of Utah professor Thomas Reichler, senior author of the report published in the journal Nature Geoscience. "It also is not new that the troposphere impacts the ocean. But now we actually demonstrated an entire link between the stratosphere, the troposphere and the ocean."
Through the use of computer simulations based on 30 years of weather data, the researchers were able to show that shifts in the winds 15 to 30 miles high in the stratosphere can impact ocean circulation as far as a mile below the surface that in turn drives weather patterns.
During the winter, a vortex of 80-mph polar winds swirls above the polar region in a counterclockwise direction. However, about every two years these winds can weaken or even begin spinning clockwise when temperatures rise.
"These are catastrophic rearrangements of circulation in the stratosphere," Reichler said. "Breakdown of the polar vortex can affect circulation in the troposphere all the way down to the surface."
Scientists have known for years that stratospheric winds cause changes in the troposphere, where weather occurs. However, this study breaks new ground by showing how these winds influence ocean circulation.
At the ocean´s surface, the wind patterns force the circulation of cold salt water that sinks and “drives the three-dimensional oceanic conveyor belt circulation” in a process called “downwelling,” Reichler added.
The effects of these interactions are most pronounced in the region around Greenland, which scientists have dubbed the Achilles heel of the Atlantic.
"This area where downwelling occurs is quite susceptible to cooling or warming from the troposphere,” Reichler said. “If the water is close to becoming heavy enough to sink, then even small additional amounts of heating or cooling from the atmosphere may be imported to the ocean and either trigger downwelling events or delay them.”
Both historical data and the 4,000 years worth of computer simulations run by the researchers support this model of decades-long climate patterns. During the 1980s and 2000s, the polar vortex was weakened by warming trends, but the 1990s saw a resurgence of these forces.
"The weakening and strengthening of the stratospheric circulation seems to correspond with changes in ocean circulation in the North Atlantic," Reichler said, and added “the computer model showed that when we have a series of these polar vortex changes, the ocean circulation is susceptible to those stratospheric events.”
According to the professor, the study´s results point out the complex nature of climate patterns and how human activities might affect these patterns in many areas along the way.
"If we as humans modify the stratosphere, it may — through the chain of events we demonstrate in this study — also impact the ocean circulation. Good examples of how we modify the stratosphere are the ozone hole, and also fossil-fuel burning that adds carbon dioxide to the stratosphere," Reichler concluded.
"These changes to the stratosphere can alter the ocean, and any change to the ocean is extremely important to global climate."