If Earth had a pulse it would be The Atlantic Meridional Overturning Circulation, a swirling of ocean currents that carry tropical heat north to polar waters.This global heartbeat has slowed to a pace not seen since the last millennium. Research based on a variety of indices now supports the view that the weakening is not a trivial one and that a critical transition is in sight.Climate scientist Niklas Boers, Freie Universitt Berlin, Germany has just released a study that shows how the AMOC is on the verge of reaching a tipping point.Recent research published in Nature Climate Change by his team confirms that the AMOC can be relatively stable in two distinct states.One is the strong form we have grown to love over the course of modern history. It is driven by large amounts of warm water from tropics that evaporates on its journey north, becoming more dense with each drop in temperature and increase in salinity.This not only moves heat energy around the oceans and atmosphere, but it also keeps the mixture of minerals and organic compound that fertilize the ocean waters free from stagnation.The other system is far less strong, with slow waters taking their time to distribute warm, nutrient rich water around the Atlantic.Although studies on the AMOC were not common in the past, recent evidence suggests that this enormous conveyor belt may be less effective.The complexity of climate models makes it difficult to determine the cause of the apparent shift. This leaves room for debate about the prognosis as well as the implications. Evidence is mounting that melting ice melts faster, causing an increase in salinity and temperature that puts a halt to the entire system.Some models suggest that the AMOC may tolerate some slowdown and remain relatively stable as the poles melt. It might even return to its former glory without too much trouble.However, not everyone agrees. Boers' study suggests that there are good reasons to believe the current network could not only collapse but become weaker and more stable.Boers writes that "the results presented here thus show that the recently discovered AMOC decrease during the past decades is not a fluctuation associated with low-frequency climate variability oder a linear response to rising temperatures.""Rather, these findings suggest that the decline could be associated with an almost total loss of stability in the AMOC over time. It is possible that the AMOC could be nearing a critical transition into its weak circulation mode."We don't know the full consequences of a sustained and drastic weakening in currents. It might cool the planet and counteract the worst effects of global warming by taking certain measures.This isn't always the good news that you might expect. Massive shifts in energy and nutrients distributions in the Atlantic's currents could have devastating consequences for weather systems across Europe and the Americas. This would have massive economic impacts on everything, from tourism to agriculture.For example, what the Amazon may gain in rain, Europe could lose in productivity.Boer believes his modeling indicates that the AMOC is near tipping point, but it's impossible to predict the timing of geological events. A sudden change could take many years, if it is not decades.It is not difficult to see how our actions could lead us closer towards the inevitable.Damian Carrington, from The Guardian, said that Boer stated that the only way to keep emissions down is to keep them as low as possible."The probability of this highly-impacting event occurring increases with every gram CO 2 we add to the atmosphere."This research was published by Nature Climate Change.
