How will the North Atlantic Current (Gulf stream) be affected by climate change?

Question

How will the North Atlantic Current (Gulf stream) be affected by climate change?

Answer 1

The powerful ocean current that bathes Britain and northern Europe in warm waters from the tropics has weakened dramatically in recent years, a consequence of global warming that could trigger more severe winters and cooler summers across the region.

Researchers on a scientific expedition in the Atlantic Ocean measured the strength of the current between Africa and the east coast of America and found that the circulation has slowed by 30% since a previous expedition 12 years ago.

The current, which drives the Gulf Stream, delivers the equivalent of 1m power stations-worth of energy to northern Europe, propping up temperatures by 10C in some regions. The researchers found that the circulation has weakened by 6m tonnes of water a second. Previous expeditions to check the current flow in 1957, 1981 and 1992 found only minor changes in its strength, although a slowing was picked up in a further expedition in 1998.

If the current remains as weak as it is, temperatures in Britain are likely to drop by an average of 1C in the next decade. Models show that if it shuts down completely, 20 years later, the temperature is 4C to 6C degrees cooler over the UK and north-western Europe.

The current is essentially a huge oceanic conveyor belt that transports heat from equatorial regions towards the Arctic circle. Warm surface water coming up from the tropics gives off heat as it moves north until eventually, it cools so much in northern waters that it sinks and circulates back to the south. There it warms again, rises and heads back north.

Global warming weakens the circulation because increased meltwater from Greenland and the Arctic icesheets along with greater river run-off from Russia pour into the northern Atlantic and make it less saline which in turn makes it harder for the cooler water to sink, in effect slowing down the engine that drives the current.

Uncertainties in climate change models mean that the overall impact on Britain of a slowing down in the current are hard to pin down. We know that if the current slows down, it will lead to a drop in temperatures in Britain and northern Europe of a few degrees, but the effect isn't even over the seasons. Most of the cooling would be in the winter, so the biggest impact would be much colder winters.

The final impact of any cooling effect will depend on whether it outweighs the global warming that, paradoxically, is driving it. According to climate modellers, the drop in temperature caused by a slowing of the Atlantic current will, in the long term, be swamped by a more general warming of the atmosphere.

Answer 2

The moderate climate of the US will cool.

Answer 3

No one knows.  It could change, or it could remain the same.  Either way, global warming will be blamed as the cause.

Answer 4

The Normal US climate will cool