The Great Ocean Conveyor

The Earth’s oceans and atmosphere act like a huge transport system, moving heat from the warmer regions around the equator to the colder areas at the poles. These sea currents and winds follow established patterns which encircle the globe and are known as the Great Ocean Conveyor Belt.

One of these conveyors, the Gulf Stream (the North Atlantic Thermohaline Conveyor), carries warm water from the tropics (around the Caribbean) to North West Europe. One arm of this Gulf Stream, the North Atlantic Drift, flows up the west coast of Scotland and is responsible for maintaining a temperate climate.

Scotland’s climate is, as a result of the conveyor, very much warmer than other parts of the world at the same latitude. Edinburgh is at the same latitude as Hudson Bay in North America, where the sea freezes in winter. Thousands of species of exotic plants flourish at Inverewe Garden in Wester Ross, farther north than Moscow where winter temperatures regularly fall to -20ºC.

It is possible that the Gulf Stream will decrease in strength over the next 100 years as a result of global warming. But models suggest that even with decreases of as much as a quarter of its current strength and the cooling effect this will have the overall result of climate change is expected to be a warmer Scotland.

There is however a scenario in which the conveyer could stop completely.

About 8000 years ago a vast lake, dammed behind an ice barrier where the St Laurence River now is, suddenly burst. This allowed billions of litres of cold freshwater into the North Atlantic.

This stopped the Gulf Stream, plunging what is now Scotland into a 1000-year mini ice age. The drained remains of the ice-dammed lake are now the North American Great Lakes.

It has been noted that the rapid melting of the Greenland Ice cap could lead to the Gulf Stream shutting down.  While this scenario is judged to be unlikely and certainly not within the next 100 years it is never the less one of the possible future consequences of climate change.

Photo credit: Tracey Dixon

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