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The Butterfly Effect and the St. John River

  • May 2, 2008 12:19 PM |  
  • By Quirks

By Bob McDonald, host of the CBC science radio program Quirks & Quarks.

Edward Lorenz, a famous American mathematician, once posed the question, “Does the flap of a butterfly’s wings in Brazil set off a tornado in Texas?” He was referring to an effect seen in chaos theory, where a small effect has huge consequences later on, a condition known as “sensitive dependence on early conditions.” Well, the butterfly-to-tornado effect has not been observed directly yet, but a similar long chain of events, beginning months ago on the other side of the world, has led to the flooding of the St. John River.

It’s a prime example of how far-reaching environmental effects can be.

The sequence began not quite with a butterfly’s wing, but it did involve a breeze. Quite a steady breeze actually, as the trade winds blew westward this year across the Pacific Ocean from Central America towards Asia. The winds carried the warm upper layer of ocean water over to the other side of the Pacific, which drew cold water up from the depths along this side of the ocean to replace it.

This cold body of water sitting off the west coast of the Americas is La Nina, an effect that comes along every three to five years. It’s the opposite of El Nino, which is a warm current, and both are part of a general sloshing back and forth across the Pacific called the southern oscillation. The large blob of cool water sitting along the West Coast this year altered the weather patterns to the north, especially the position of the jet stream.

The boundary between the cold air at the top of the world and the warm air around the middle of the planet is a meandering river of fast moving air that circles the globe. You see the jet stream on national weather maps as a broad curving line that either dips up or down across the continent.

This year, La Nina pushed part of the stream northwards towards Alaska, which forced the stream east of that to dip downwards over the central part of the continent, then back up again towards the east. It looked like a big “S” on its side. This huge tongue of cold air hanging down over the land was responsible for the record cold temperatures on the Prairies this winter.

Storms tend to follow the course of the jet stream, so while it sat stalled over the continent, just about every major winter storm was steered from the central U.S. up towards southern Ontario, along the St. Lawrence Valley and on to the Maritimes, leaving behind record amounts of snow.

Well, spring comes, snow melts, rivers flood. The St. John River has a huge drainage area covering 55,000 square kilometers, which can hold onto a lot of snow, which then turned into lot of water, which is now trying to squeeze through the narrow river channel.

Who would have thought that wind over the Pacific would cause flooding in a river that flows into the Atlantic?

By the way, the flooding of the river is not a natural disaster; it’s a human problem. Flooding is a necessary part of river ecology. It replenishes soils and rejuvenates wetlands. But people like to live near water, so we build walls and dykes, hoping to keep the water under control, which is, of course, next to impossible. The real ecological disaster will come from all the old paint cans, and packages of chemicals and fertilizers people keep in their garages and basements, as well as sewage and other waste that will be picked up by the flood waters, creating a contaminated plume downstream.

John Muir, a conservationist in the early 1900s wrote, “Tug on anything at all and you will find it is connected to everything else in the universe.”

The butterfly effect continues.

- Bob McDonald

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