Stratospheric winds influence ocean currents, scientists say

Changes in wind direction 15 to 30 miles above Earth’s surface can affect mile-deep currents in the North Atlantic by striking an oceanic “Achilles’ heel,” according to atmospheric scientists.

The discovery, published Monday in the journal Nature Geoscience, carries implications for the study of Earth’s climate and how we predict its change.

Scientists have long understood that events in Earth’s stratosphere -- that layer of atmosphere that begins 6 miles above Earth’s surface and extends another 25 miles in height -- influences events in the lower troposphere, where weather occurs.

Scientists have also understood that sea currents influence climate, and that sea currents are dictated heavily by changes in water temperature and salt content.

Before now, however, scientists had not clearly demonstrated a link between events in the higher stratosphere to sea currents, according to lead study author Thomas Reichler, a University of Utah atmospheric scientist.

By using weather observations and supercomputer simulations, researchers found that periodic changes in the temperature, speed and direction of polar vortex winds within the stratosphere trigger changes in the lower troposphere, which then appeared to affect the ocean.

Reichler and his colleagues cite a specific area of the North Atlantic, just south of Greenland, as being particularly sensitive to this influence. The area is called the downwelling region, where water becomes cold and salty enough to sink, and helps drive current patterns.

However, if this area gets warmed or cooled by atmospheric events originating in the stratosphere, the downwelling process can be slowed or accelerated.

Because of this sensitivity, Reichler calls the area the “Achilles’ heel of the North Atlantic.”

“If we as humans modify the stratosphere, it may -- through the chain of events we demonstrate in this study -- also impact the ocean circulation,” Reichler said. “Good examples of how we modify the stratosphere are the ozone hole and also fossil-fuel burning that adds carbon dioxide to the stratosphere. These changes to the stratosphere can alter the ocean, and any change in the ocean is extremely important to global climate.”

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