The butterfly effect

What do the English riots and the Sulzberger ice shelf in Antarctica have in common? Dropping a stone in a pond causes ripple to emanate from the source, getting bigger and bigger the further away from the source they get. And – as the saying goes – a butterfly flapping its wings in Brazil, causes a tornado in Texas.

The ripple effect and the butterfly effect – two examples of small changes causing large and far-reaching effects. The riots many of us have experienced in recent weeks are another prime example of this: the shooting of a single man caused riots in his home of Tottenham, which sparked copycat rioting and looting in several towns and cities around the country.

But while rioting is likely to be sporadic, these effects can be observed more regularly in science, in particular in geological events.

The March 2011 earthquake in Japan and the ensuing tsunami caused ripples around the world. Although the event itself was huge – the earthquake measured 9.0 on the moment magnitude scale – the single earthquake was so powerful that it caused icebergs to break away from the Sulzberger ice shelf in Antarctica over 8,000 miles away.

It gave scientists a unique opportunity to study cause and effect straight from the source. Usually, when new icebergs are seen, scientists go looking for the source, but this time the source was known – they just had to find the effect.

“In the past, we’ve had calving events where we’ve looked for the source. It’s a reverse scenario – we see a calving and we go looking for a source,” said Kelly Brunt. “We knew right away this was one of the biggest events in recent history – we knew there would be enough swell. And this time we had a source.”

Brunt, a cryosphere specialist at the Goddard Space Flight Centre, and colleagues looked south – really far south, over 8,000 miles away to the Antarctic. Using multiple satellite images, they observed new icebergs floating off to sea shortly after the sea swell of the tsunami reached the area – 18 hours after the original event.

The ice that broke away together equalled an area twice the size of Manhattan, and according to historical record, this particular piece of ice hadn’t budged in at least 46 years before the tsunami came along.

“It’s a pretty big chunk of ice that calved because of an earthquake 13,000km away,” said Brunt. “I think that’s pretty cool.”

However, such a clear cause and effect is rare when trying to tease out global geological events. Yet a prime example of this – weather predictions – may have just got a little bit more accurate.

In 1961, Edward Lorenz was using computer modelling to rerun a weather prediction. When imputing an important variable, instead of typing in 0.506127, he keyed in 0.506 – and the prediction was completely different. This small change led to a hugely different effect.

He published his findings in New York Academy of Sciences and over the years gave several talks about how tiny changes in the atmosphere – caused by the flapping of a butterfly’s wings – might alter weather, in particular the path of a tornado.

Just last month, meteorologists in Manchester updated a weather model that predicts behaviour in low pressure systems. Some of the biggest storms in the UK – like the Great Storm of October 1987 – didn’t fit the previous model first proposed in the 1920s.

The model states that when a storm occludes or evolves, it will automatically begin to weaken and pose little danger of severe weather. But we know this is not the case – occluded storms still contain strong winds and areas of heavy rain.

The research has resulted in a new model called ‘wrap up’, which emphasises that wind around the occluding storm wraps up the low pressure system in an anticlockwise-spiralling pattern.

So it’s clear that a small change can have a large and far-reaching effect – even if it’s not always immediately noticeable.

Author: Kerry Taylor Smith Staff Writer, Laboratory News