Gulf Stream Collapse
The Gulf Stream has slowed by 6 million tonnes of water per second over the past 30 years. Many scientists are worried that this portends a collapse and have applied computer models to work out the alternatives. These show there is a 50% chance the current will collapse totally when global temperatures rise by 3°C.
The waters that flow from the Antarctic to the north on the surface of the Atlantic are warm and lose water by evaporating, and therefore get saltier. Salt water is heavier than fresh water and when it reaches the north Atlantic it would sink were it not that the cold water from the arctic is denser still. The arctic water sinks under the warm and provides the force that drives the conveyor and creates the Gulf Stream.
One scenario presented recently to the Pentagon posits that a Gulf Stream collapse could begin in a few years. That massive current of warm water would no longer reach far into the North Atlantic. This would seriously disrupt the temperate climate of Europe and the east coast of North America. The probable outcome would be that the climate of the UK that is now 8°C warmer than the same latitudes in other parts of the world would become closer to that in Russia.
The lesser impact would be a 500mm ocean rise as water heats up.
It is not clear what type of weather would follow a collapse. Some forecasters believe the globe would continue to heat, others predict a new ice age or a global drought. The best models suggest there would be a 5°F drop over Asia and North America and up to 6°F in Europe. On the other hand there would be an increase by up to 4°F in Australia, South America, and south Africa.
Winter storms and cyclonic winds would intensify, amplifying the impact of the changes. Average annual rainfall in Europe and China could decrease by nearly 30%. Europe’s climate would then become more like Siberia’s bringing harsh conditions for agriculture.
No chance then for a reduction in heating loads, and so
CO2 emissions would increase further.