One of the key drivers of the world's climate is an area in the North Atlantic Ocean where warmer and colder water mix and swirl.
When scientists went for their first close look at this critical underwater dynamo, they found they were looking in the wrong place.
By hundreds of miles.
In this September 2018 photo provided by researcher Isabela Le Bras, mooring for measuring equipment is recovered just offshore of Greenland in the early morning with icebergs visible in the background. Scientists were studying the Atlantic Meridional Overturning Circulation (AMOC), a circulation of warm and cold waters that stretches from around Greenland south to beyond the tip of Africa and into the Indian Ocean.
The consequences are not quite yet understood, but eventually it could change forecasts of one of the worst-case global warming scenarios - still considered unlikely this century - in which the mixing stops and climate chaos ensues.
It's called the Atlantic Meridional Overturning Circulation , and scientists describe it as a giant ocean conveyor belt that moves water from Greenland south to beyond the tip of Africa and into the Indian Ocean.
Warm, salty water near the surface moves north and mixes with cold, fresher water near Greenland.
As that water cools and sinks it drives a slow circulation of the oceans that is critical to global climate, affecting the location of droughts and frequency of hurricanes. It also stores heat-trapping carbon dioxide deep in the ocean.
The faster it moves, the more warm water gets sent into the depths to cool.
The area where warm water turns over in the North Atlantic is considered to be the engine of the conveyor belt.
Scientists thought it was in the Labrador Sea west of Greenland.
WHAT IS THE GLOBAL OCEAN CONVEYOR BELT?
When it comes to regulating global climate, the circulation of the Atlantic Ocean plays a key role.
This is due to a constantly moving system of deep-water circulation often referred to as the Global Ocean Conveyor Belt which 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.
When it comes to regulating global climate, the circulation of the Atlantic Ocean plays a key role
This motion is fuelled by thermohaline currents - a combination of temperature and salt.
It takes 1,000 years for water to complete a continuous journey around the world.
Researchers believe that as the North Atlantic began to warm near the end of the Little Ice Age, freshwater disrupted the system, called the Atlantic Meridional Overturning Circulation (AMOC).
Arctic sea ice, and ice sheets and glaciers surrounding the Arctic began to melt, forming a huge natural tap of fresh water that gushed into the North Atlantic.
This huge influx of freshwater diluted the surface seawater, making it lighter and less able to sink deep, slowing down the AMOC system.
Researchers found the AMOC has been weakening more rapidly since 1950 in response to recent global warming.
But then a new international science team measured temperature, saltiness and the speed of ocean currents throughout the North Atlantic to try to better understand the conveyor belt.
The preliminary results after hundreds of measurements in 21 months found that engine was several hundreds of miles east of where they figured, said study lead author Susan Lozier, an ocean sciences professor at Duke University.
The study, published in Thursday's journal Science, puts it east of Greenland, closer to Scotland.
The computer simulations that predict how the climate could change in coming years didn't factor in exactly where the conveyor belt engine is, and now they may be able to.
Lozier and several outside experts said this doesn't change their trust in the models, especially because when the models are checked with what is happening in the real world, they are found to be generally accurate.
'It doesn't mean that the models are all wrong at all,' said Tom Delworth, a senior scientist at the National Oceanic and Atmospheric Administration's geophysical lab in Princeton, New Jersey.
MIT's Carl Wunsch and other outside experts said the study was helpful, but pointed out that 21 months of study is not enough to know if this different location is temporary or permanent.
Scientists have long feared that the conveyor belt could be slowing and, in a worst-case scenario, could even stop and cause abrupt and catastrophic climate change.
It is considered a potential climate tipping point that was the premise of the scientifically inaccurate 2004 disaster movie 'The Day After Tomorrow.'
In this September 2018 photo provided by researcher Isabela Le Bras, a probe which collects water samples and measures temperature, salinity and pressure is prepared for deployment on the continental shelf of Greenland. Scientists were studying the Atlantic Meridional Overturning Circulation (AMOC), a circulation of warm and cold waters that stretches from around Greenland south to beyond the tip of Africa and into the Indian Ocean.
Based on computer model studies, the United Nations' Intergovernmental Panel on Climate Change reported in an earlier study it is 'very unlikely' that the conveyor belt would collapse this century. But the Nobel Prize-winning scientific panel concluded it is likely to get about a third slower if greenhouse gas emissions continue at its current pace.
A study last year found that global warming is weakening the system, saying the conveyor belt was moving at its slowest speed in nearly 140 years of records.
'Our basic understanding that the collapse is unlikely still stands,' said Delworth, who wasn't part of the study.
'Our uncertainty about that prediction is high.'
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Main photo article One of the key drivers of the world’s climate is an area in the North Atlantic Ocean where warmer and colder water mix and swirl.
When scientists went for their first close look at this critical underwater dynamo, they found they were looking in the wrong place.
By hundreds of ...
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Dianne Reeves Online news HienaLouca
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