Unexpected Teleconnections
Spooky action at a distance in our atmosphere
Physicists who study quantum mechanics have a concept called “quantum entanglement”, where two objects separated in space can exhibit a weird connection. Einstein didn’t like the idea, deriding it as “spooky action at a distance”, but the concept he saw as impossible has since been experimentally verified.
Quantum mechanics isn’t the only place in which we see weird connections between things that are far apart. The Earth’s atmosphere also exhibits odd links between different parts of the world, known as “teleconnections” — and we’re only just beginning to understand them.
For example, you wouldn’t imagine that winter temperatures in Indianapolis have anything to do with the frequency of a particular type of high-altitude cloud in the skies high over Antarctica. But it does. Here’s a chart that shows it.
In this, deviations from normal surface temperatures in Indianapolis are plotted in blue, deviations from normal conditions in the arctic stratosphere are plotted in red and deviations from normal numbers of high-altitude noctilucent clouds are plotted in yellow. They follow each other remarkably closely.
It’s not just Indianapolis. When temperatures plunge in many northern cities around the world, noctilucent clouds disappear above Antarctica two weeks later. It seems to take almost exactly two weeks for the “signal” to travel the 14,500 miles to the South Pole.
The culprit? A “ripple effect” from stratospheric winds in the Arctic that spreads slowly across the globe, all the way down to the high atmosphere of the Antarctic.
Noctilucent clouds are the highest clouds in the atmosphere. They form about 83 kilometres in the sky, almost as high as the 100km Kármán line that separates the atmosphere and space. Made of ice crystals, they’re normally too faint to be seen but can be spotted at sunrise and sunset when they’re illuminated by sunlight that shines above the lower layers of the atmosphere.
They’re a poorly-understood phenomenon, so NASA’s AIM satellite was launched in 2007 to learn more about them — particularly how they form and their chemistry. But like many space missions, the data yielded something extra that wasn’t expected — evidence of atmospheric teleconnections.
It has been a surprise,” said James Russell, principal investigator of the AIM mission. “Years ago when we were planning the AIM mission, our attention was focused on a narrow layer of the atmosphere where noctilucent clouds form. Now we are finding out this layer manifests evidence of long-distance connections in the atmosphere far from the noctilucent clouds themselves.”
One of those connections is the aforementioned link between the Arctic stratosphere and the Antarctic mesosphere.
“Stratospheric winds over the Arctic control circulation in the mesosphere,” explains Randall. “When northern stratospheric winds slow down, a ripple effect around the globe causes the southern mesosphere to become warmer and drier, leading to fewer noctilucent clouds.”
He added: “When northern winds pick up again, the southern mesosphere becomes colder and wetter, and the noctilucent clouds return.”
Those of you in the northern hemisphere, particularly in the United States, will no doubt remember the unusual distortion of the arctic polar vortex that brought frigid conditions far south over the winter of 2013/2014. Two weeks later, at a time of year when noctilucent clouds are frequently seen in the Antarctic, they abruptly declined.
“We believe that this triggered a ripple effect that led to a decline in noctilucent clouds half-way around the world,” said Laura Holt of the University of Colorado’s Laboratory for Atmospheric and Space Physics. “This is the same polar vortex that made headlines this winter when parts of the USA experienced crippling cold and ice.”
This noctilucent cloud link is just one of many teleconnections in the atmosphere. Others we’re more familiar with include the global effects of the El Niño disturbance in the Southern Pacific, and the wide effects of the North Atlantic oscillation. But it’s likely that there are many, many more teleconnections out there that we’re unaware of and could make our weather forecasting much more accurate.
“Noctilucent clouds are a valuable resource for studying long-distance connections in the atmosphere,” says Russell, “and we’re just getting started.”
For more on teleconnections, here’s a great explainer by Science@NASA.
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