Winds 'can affect Earth's climate'

Whirling winds in the upper atmosphere can influence what happens at the bottom of the oceans and in turn affect the Earth's climate, say scientists.

Disruption of the 80mph "polar vortex" winds encircling the Arctic impacts on mile-deep ocean circulation patterns, research suggests.

Over periods of decades, this can alter the flow of warm and cold water around the planet, leading to changes in the weather.

Scientists already knew disturbances in the stratosphere are felt lower down in the troposphere, the part of the atmosphere stretching from the Earth's surface to a height of six miles or 33,000 feet.

The new research indicates that events up to 30 miles above the North Pole have an influence that extends right through the atmosphere into the deep ocean.

"We found evidence that what happens in the stratosphere matters for the ocean circulation and therefore for climate," said US expert Dr Thomas Reichler, from the University of Utah, who led the study published online in the journal Nature Geoscience.

"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. These changes to the stratosphere can alter the ocean, and any change to the ocean is extremely important to global climate."

The scientists used meteorological and ocean data collected over the past 30 years, together with supercomputer simulations, to show the link between the polar vortex and rhythmic changes in deep sea circulation patterns. "The weakening and strengthening of the stratospheric circulation seems to correspond with changes in ocean circulation in the north Atlantic," said Dr Reichler.

In winter, the Arctic polar vortex spins counter-clockwise around the North Pole. But every two years on average, the stratospheric air is suddenly disrupted and the vortex gets warmer and weaker. Sometimes it even shifts direction and starts turning clockwise.

The effects can last up to two months. Dr Reichler's team showed how they were felt all the way down to the ocean and mirrored by changes in the speed of the Atlantic Meridional Overturning Circulation (AMOC). The AMOC is a key element of the global circulation system that acts like a conveyor belt moving water around the planet. Computer simulations showed a decadal on-off pattern of correlated changes in the polar vortex, atmospheric pressure oscillations over the north Atlantic, and changes in circulation currents more than a mile below the ocean surface.