The winds of the stratosphere reshape deep ocean currents

We know Earth's countless geological and climatological processes are interconnected, but this connection is particularly incredible. Wind patterns 15 to 30 miles above the Earth's surface can wreak havoc on deep ocean currents... and Earth's climate as a whole.

That's the finding of a research team led by the University of Utah's Thomas Reichler. The stratosphere is the next level up in the atmosphere above the troposphere, which is where we and pretty much all known life on Earth are found. The stratosphere, on the other hand, extends from 6 to 30 miles above the planet's surface, and it's in the upper stratosphere that these current-altering winds are found. Professor Reichler explains the importance of the find:

"We found evidence that what happens in the stratosphere matters for the ocean circulation and therefore for climate. It is not new that the stratosphere impacts the troposphere. 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."

The winds of the stratosphere reshape deep ocean currentsS

Their findings are based both on direct observation of climate patterns and on 4,000 years of simulated weather using a supercomputer. The phenomenon they discovered is known as stratospheric sudden warming. The effect is kicked off when the polar vortex winds that swirl in the upper stratosphere above the Arctic start to decrease in speed from their usual average of 80 mph, sometimes even reversing direction. This phenomenon lasts about 60 days, and the researchers found that such events were often followed by a similar slowdown of deep ocean currents in the north Atlantic.

So why exactly does this matter? Professor Reichler explains:

"These changes to the stratosphere can alter the ocean, and any change to the ocean is extremely important to global climate. The North Atlantic is particularly important for global ocean circulation, and therefore for climate worldwide. In a region south of Greenland, which is called the downwelling region, water can get cold and salty enough – and thus dense enough – so the water starts sinking. [This] drives the three-dimensional oceanic conveyor belt circulation. What happens in the Atlantic also affects the other oceans. This area where downwelling occurs is quite susceptible to cooling or warming from the troposphere. 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. [This region is] the Achilles heel of the North Atlantic."

Professor Reichler has been tracking the connection between the polar vortex and the currents of the North Atlantic since the 1980s, and the supercomputer simulations have helped clarify that the two phenomena are indeed linked. It's an important finding because, as Reichler points out, we have the ability to modify the stratosphere, which very much includes the ozone hole and the added carbon that comes from the consumption of fossil fuels. It's not exactly news that those activities aren't helping the planet, but this new finding reveals just how wide-ranging the effects of messing with the stratosphere can actually be. For more, check out the University of Utah or the original paper at Nature Geoscience.

Top image by NASA Goddard Photo and Video via Flickr. Diagram by Thomas Reichler, University of Utah.