Atlantic Ocean circulation at weakest point in more than 1,500 years

http://www.realclimate.org/index.php/archives/2018/04/stronger-evidence-for-a-weaker-atlantic-overturning-circulation/

The system that regulates our climate and weather in the Atlantic is getting weaker! 

It sounds paradoxical when one thinks of the shock-freeze scenario of the Hollywood film The Day After Tomorrow: a study by Duchez et al. (2016) shows that cold in the North Atlantic correlates with summer heat in Europe. This is due to the fact that the heat transport in the Atlantic has not yet decreased strongly enough to cause cooling also over the adjacent land areas – but the cold of the sea surface is sufficient to influence the air pressure distribution. It does that in such a way that an influx of warm air from the south into Europe is encouraged. In summer 2015, the subpolar Atlantic was colder than ever since records began in the 19th century – associated with a heat wave in Europe. Haarsma et al (2015) argue on the basis of model calculations that the weakening of the AMOC will be the main cause of changes in the summer circulation of the atmosphere over Europe in the future. Jackson et al (2015) found that the slowdown could lead to increased storm activity in Central Europe. And a number of studies suggest that if the AMOC weakens, sea levels on the US coast will rise more sharply (e.g. Yin et al. 2009). The impacts are currently being further researched, but a further AMOC slowdown cannot be considered good news. Yet, although the oscillations seen in Fig. 2 suggest the AMOC may well swing up again for a while, a long-term further weakening is what we have to expect if we let global warming continue for much longer.

When it comes to regulating global climate, the circulation of the Atlantic Ocean plays a key role. The constantly moving system of deep-water circulation, sometimes referred to as the Global Ocean Conveyor Belt, sends warm, salty Gulf Stream water to the North Atlantic where it releases heat to the atmosphere and warms Western Europe. The cooler water then sinks to great depths and travels all the way to Antarctica and eventually circulates back up to the Gulf Stream.